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Gerald T. Ankley - One of the best experts on this subject based on the ideXlab platform.
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comparison of fathead Minnow ovary explant and h295r cell based steroidogenesis assays for identifying endocrine active chemicals
Ecotoxicology and Environmental Safety, 2007Co-Authors: Daniel L Villeneuve, Gerald T. Ankley, Elizabeth A Makynen, Lindsey S Blake, Katie J Greene, Eric Higley, John L Newsted, John P GiesyAbstract:An in vitro steroidogenesis assay using H295R human adenocarcinoma cells has been suggested as a possible alternative to gonad explant assays for use as a Tier I screening assay to detect endocrine active chemicals capable of modulating steroid hormone synthesis. This study is one of the first to investigate the utility of the H295R assay for predicting effects and/or understanding mechanisms of action across species and tissues. Six chemicals, including one selective aromatase inhibitor (fadrozole), four fungicides (fenarimol, ketoconazole, prochloraz, and vinclozolin), and one herbicide (prometon), were tested in both the H295R steroidogenesis assay, and an in vitro steroidogenesis assay using fathead Minnow ovary explants. All six chemicals caused significant alterations in 17β-estradiol (E2) and/or testosterone (T) production in vitro. Effects of ketoconazole, prochloraz, and prometon were similar in both assays. However, there were differences in the profile of responses for T for fadrozole and fenarimol, and for T and E2 for vinclozolin. In terms of sensitivity, steroid production in the H295R assay was most sensitive for detecting the effects of fadrozole, fenarimol, and prochloraz, but was less sensitive than the fathead Minnow ovary explant assay to the effects of ketoconazole and vinclozolin. The H295R assay was consistently less variable (among replicates) than the fathead Minnow ovary explant assay. However, the ovary explant assay was more predictive of in vivo effects of the six chemicals on fathead Minnows than the H295R system. Further characterization of autoregulatory capacities, interaction of steroid-hormone receptor pathways with steroidogenesis, and metabolic capabilities of each system are needed for either system to provide clear and informative insights regarding a chemical's mechanism of action. Overall, however, results of this study suggest that both the H295R and fathead Minnow ovary explant assays have utility for identifying endocrine-active chemicals in screening-type applications.
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ketoconazole in the fathead Minnow pimephales promelas reproductive toxicity and biological compensation
Environmental Toxicology and Chemistry, 2007Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Lindsey S Blake, Katie J Greene, Rodney D Johnson, Daniel L VilleneuveAbstract:: Ketoconazole (KTC) is a model pharmaceutical representing imidazole and triazole pesticides, which inhibit fungal growth through blocking a cytochrome P450 (CYP)-mediated step in ergosterol biosynthesis. Several of these fungicides have been shown to be reversible inhibitors of CYPs in vertebrates (primarily mammals), including CYP isoforms involved in the pathway that converts cholesterol to active sex steroids. In these studies, we assessed the effects of KTC on aspects of steroidogenesis and reproductive function in the fathead Minnow (Pimephales promelas). Exposure of spawning adults to the fungicide for 21 d significantly decreased egg production at a water concentration as low as 25 microg/L. Despite evidence of reduced ex vivo testosterone production by gonads from KTC-exposed fathead Minnows, circulating plasma concentrations of sex steroids (testosterone, 17beta-estradiol) were not affected. Exposure to KTC caused an increase in the gonadosomatic index in both sexes and, in males, the fungicide caused a marked proliferation of interstitial (Leydig) cells. In addition, mRNA transcripts for two key steroidogenic enzymes, cytochrome P450 side-chain cleavage (CYP11A) and cytochrome P450 c17alpha hydroxylase/17,20 lyase (CYP17), were elevated by exposure to KTC. Both the changes in transcript levels and proliferation of gonad tissue represent potential adaptive or compensatory responses to impaired steroidogenic capacity. Overall our data indicate that, although KTC does adversely affect steroidogenesis and reproduction in the fathead Minnow, the fish can compensate to some degree to mitigate effects of the fungicide. This has important implications for the interpretation of data from tests with endocrine-active chemicals.
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linkage of biochemical responses to population level effects a case study with vitellogenin in the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2007Co-Authors: David H Miller, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Daniel L Villeneuve, Elizabeth J Durhan, Gerald T. AnkleyAbstract:A challenge in the field of ecotoxicology is the linkage of alterations at molecular and biochemical levels of organization to adverse outcomes in individuals and populations. In the present study, a predictive relationship between plasma vitellogenin (VTG) concentration and fecundity in female fathead Minnows (Pimephales promelas) was derived from 21-d laboratory toxicity tests with five chemicals (17β-trenbolone, 17α-trenbolone, prochloraz, fenarimol, and fadrozole) that inhibit VTG production through different mechanisms. Because VTG is key to egg production in female oviparous animals, changes in the lipoprotein could, theoretically, serve as an indicator of reproductive success. Regression of fecundity versus VTG concentration from the various studies yielded a highly significant linear model (fecundity = −0.042 + 0.95-VTG, p < 0.01, r2 = 0.88). This relationship was integrated into a population model to translate changes in VTG concentrations of female fathead Minnows to alterations in population growth. The model predicted relatively profound effects on population size offish experiencing moderate decreases in vitellogenesis. For example, a fathead Minnow population at a carrying capacity exposed to a chemical stressor that causes a 25% decrease in VTG concentration in females from baseline values would exhibit a 34.6% projected decrease in size after two years of exposure and reach an equilibrium population size that was only 30.2% of the preexposed population. Overall, the current study provides an example of how changes in a biomarker (VTG concentration) can be quantitatively translated into adverse effects at the individual and population levels.
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Evaluation of a commercial kit for measuring vitellogenin in the fathead Minnow (Pimephales promelas).
Ecotoxicology and Environmental Safety, 2006Co-Authors: Kathleen M Jensen, Gerald T. AnkleyAbstract:Vitellogenin (vtg) concentrations in oviparous animals such as fish represent an integrated indicator of the status of the reproductive endocrine system. As such, vtg is a common measurement endpoint in tests designed to detect certain classes of endocrine-disrupting chemicals (EDCs). The most common approach to measuring vtg is via enzyme-linked immunosorbent assays (ELISAs). However, because labs testing EDCs in fish often use slightly different ELISAs (e.g., in terms of antibodies, binding antigens, standards), results among studies are not always comparable. One approach to obviating this would be for researchers to use standardized ELISA kits from a common source(s). The fathead Minnow (Pimephales promelas) is a small fish model commonly used for EDC testing. The purpose of this study was to evaluate a recently developed commercial ELISA kit for measuring vtg in the fathead Minnow. The commercial ELISA, based on a monoclonal antibody to fathead Minnow vtg, was compared to an ELISA that utilizes a fathead Minnow polyclonal antibody, which has been used extensively in our lab and others for several years. Plasma samples for this comparison came from three studies in which fathead Minnows had been exposed to different model EDCs, including an androgen (17β-trenbolone), an anti-androgen (flutamide), and two CYP19 (aromatase) inhibitors (prochloraz, fadrozole). Results obtained using the two different ELISA methods were consistently similar.
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reproductive and developmental toxicity and bioconcentration of perfluorooctanesulfonate in a partial life cycle test with the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2005Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Richard L Leino, Douglas W Kuehl, Ann Linnum, Dan A VilleneuveAbstract:Perfluorooctanesulfonate (PFOS) is a widespread environmental contaminant emanating from the production and/or metabolism of fluorinated chemicals with a variety of applications. The goal of this work was to assess the toxicity and bioconcentration of PFOS in the fathead Minnow (Pimephales promelas). Sexually mature fish were exposed via the water for 21 d to 0 (control), 0.03, 0.1, 0.3, or 1 mg PFOS/L, and effects on reproductive capacity and endocrinology were assessed. To determine possible developmental effects, a subset of embryos from parental exposures at each test concentration were held for an additional 24 d in the same PFOS treatments. A concentration of 1 mg PFOS/L was lethal to adults within two weeks. The 21-d 50% effect concentration (95% confidence interval) for effects on fecundity of the fish was 0.23 (0.19–0.25) mg PFOS/L. Exposure to PFOS caused various histopathological alterations, most prominently in ovaries of adult females. Adult males exposed to 0.3 mg PFOS/L for 21 d exhibited decreased aromatase activity and elevated concentrations of plasma 11-ketotestosterone and testosterone. No significant adverse effects on survival or growth were observed in developing fathead Minnows held for 24 d at PFOS concentrations up to 0.3 mg/L. Adult fathead Minnows readily accumulated PFOS from the water. The largest concentrations of PFOS were in blood, followed by liver and then gonad; for all tissues, females accumulated higher concentrations than males. Water and tissue concentrations of PFOS associated with effects in this study exceeded those reported for samples collected from the field by two to three orders of magnitude, suggesting that the current risk of PFOS on aspects offish reproduction and development assessed in this study would be small.
Kathleen M Jensen - One of the best experts on this subject based on the ideXlab platform.
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ketoconazole in the fathead Minnow pimephales promelas reproductive toxicity and biological compensation
Environmental Toxicology and Chemistry, 2007Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Lindsey S Blake, Katie J Greene, Rodney D Johnson, Daniel L VilleneuveAbstract:: Ketoconazole (KTC) is a model pharmaceutical representing imidazole and triazole pesticides, which inhibit fungal growth through blocking a cytochrome P450 (CYP)-mediated step in ergosterol biosynthesis. Several of these fungicides have been shown to be reversible inhibitors of CYPs in vertebrates (primarily mammals), including CYP isoforms involved in the pathway that converts cholesterol to active sex steroids. In these studies, we assessed the effects of KTC on aspects of steroidogenesis and reproductive function in the fathead Minnow (Pimephales promelas). Exposure of spawning adults to the fungicide for 21 d significantly decreased egg production at a water concentration as low as 25 microg/L. Despite evidence of reduced ex vivo testosterone production by gonads from KTC-exposed fathead Minnows, circulating plasma concentrations of sex steroids (testosterone, 17beta-estradiol) were not affected. Exposure to KTC caused an increase in the gonadosomatic index in both sexes and, in males, the fungicide caused a marked proliferation of interstitial (Leydig) cells. In addition, mRNA transcripts for two key steroidogenic enzymes, cytochrome P450 side-chain cleavage (CYP11A) and cytochrome P450 c17alpha hydroxylase/17,20 lyase (CYP17), were elevated by exposure to KTC. Both the changes in transcript levels and proliferation of gonad tissue represent potential adaptive or compensatory responses to impaired steroidogenic capacity. Overall our data indicate that, although KTC does adversely affect steroidogenesis and reproduction in the fathead Minnow, the fish can compensate to some degree to mitigate effects of the fungicide. This has important implications for the interpretation of data from tests with endocrine-active chemicals.
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linkage of biochemical responses to population level effects a case study with vitellogenin in the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2007Co-Authors: David H Miller, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Daniel L Villeneuve, Elizabeth J Durhan, Gerald T. AnkleyAbstract:A challenge in the field of ecotoxicology is the linkage of alterations at molecular and biochemical levels of organization to adverse outcomes in individuals and populations. In the present study, a predictive relationship between plasma vitellogenin (VTG) concentration and fecundity in female fathead Minnows (Pimephales promelas) was derived from 21-d laboratory toxicity tests with five chemicals (17β-trenbolone, 17α-trenbolone, prochloraz, fenarimol, and fadrozole) that inhibit VTG production through different mechanisms. Because VTG is key to egg production in female oviparous animals, changes in the lipoprotein could, theoretically, serve as an indicator of reproductive success. Regression of fecundity versus VTG concentration from the various studies yielded a highly significant linear model (fecundity = −0.042 + 0.95-VTG, p < 0.01, r2 = 0.88). This relationship was integrated into a population model to translate changes in VTG concentrations of female fathead Minnows to alterations in population growth. The model predicted relatively profound effects on population size offish experiencing moderate decreases in vitellogenesis. For example, a fathead Minnow population at a carrying capacity exposed to a chemical stressor that causes a 25% decrease in VTG concentration in females from baseline values would exhibit a 34.6% projected decrease in size after two years of exposure and reach an equilibrium population size that was only 30.2% of the preexposed population. Overall, the current study provides an example of how changes in a biomarker (VTG concentration) can be quantitatively translated into adverse effects at the individual and population levels.
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Evaluation of a commercial kit for measuring vitellogenin in the fathead Minnow (Pimephales promelas).
Ecotoxicology and Environmental Safety, 2006Co-Authors: Kathleen M Jensen, Gerald T. AnkleyAbstract:Vitellogenin (vtg) concentrations in oviparous animals such as fish represent an integrated indicator of the status of the reproductive endocrine system. As such, vtg is a common measurement endpoint in tests designed to detect certain classes of endocrine-disrupting chemicals (EDCs). The most common approach to measuring vtg is via enzyme-linked immunosorbent assays (ELISAs). However, because labs testing EDCs in fish often use slightly different ELISAs (e.g., in terms of antibodies, binding antigens, standards), results among studies are not always comparable. One approach to obviating this would be for researchers to use standardized ELISA kits from a common source(s). The fathead Minnow (Pimephales promelas) is a small fish model commonly used for EDC testing. The purpose of this study was to evaluate a recently developed commercial ELISA kit for measuring vtg in the fathead Minnow. The commercial ELISA, based on a monoclonal antibody to fathead Minnow vtg, was compared to an ELISA that utilizes a fathead Minnow polyclonal antibody, which has been used extensively in our lab and others for several years. Plasma samples for this comparison came from three studies in which fathead Minnows had been exposed to different model EDCs, including an androgen (17β-trenbolone), an anti-androgen (flutamide), and two CYP19 (aromatase) inhibitors (prochloraz, fadrozole). Results obtained using the two different ELISA methods were consistently similar.
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reproductive and developmental toxicity and bioconcentration of perfluorooctanesulfonate in a partial life cycle test with the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2005Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Richard L Leino, Douglas W Kuehl, Ann Linnum, Dan A VilleneuveAbstract:Perfluorooctanesulfonate (PFOS) is a widespread environmental contaminant emanating from the production and/or metabolism of fluorinated chemicals with a variety of applications. The goal of this work was to assess the toxicity and bioconcentration of PFOS in the fathead Minnow (Pimephales promelas). Sexually mature fish were exposed via the water for 21 d to 0 (control), 0.03, 0.1, 0.3, or 1 mg PFOS/L, and effects on reproductive capacity and endocrinology were assessed. To determine possible developmental effects, a subset of embryos from parental exposures at each test concentration were held for an additional 24 d in the same PFOS treatments. A concentration of 1 mg PFOS/L was lethal to adults within two weeks. The 21-d 50% effect concentration (95% confidence interval) for effects on fecundity of the fish was 0.23 (0.19–0.25) mg PFOS/L. Exposure to PFOS caused various histopathological alterations, most prominently in ovaries of adult females. Adult males exposed to 0.3 mg PFOS/L for 21 d exhibited decreased aromatase activity and elevated concentrations of plasma 11-ketotestosterone and testosterone. No significant adverse effects on survival or growth were observed in developing fathead Minnows held for 24 d at PFOS concentrations up to 0.3 mg/L. Adult fathead Minnows readily accumulated PFOS from the water. The largest concentrations of PFOS were in blood, followed by liver and then gonad; for all tissues, females accumulated higher concentrations than males. Water and tissue concentrations of PFOS associated with effects in this study exceeded those reported for samples collected from the field by two to three orders of magnitude, suggesting that the current risk of PFOS on aspects offish reproduction and development assessed in this study would be small.
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characterization of responses to the antiandrogen flutamide in a short term reproduction assay with the fathead Minnow
Aquatic Toxicology, 2004Co-Authors: Kathleen M Jensen, Joseph J. Korte, Michael D Kahl, Elizabeth A Makynen, Richard L Leino, Brian C Butterworth, Gerald T. AnkleyAbstract:Abstract A short-term reproduction assay with the fathead Minnow (Pimephales promelas) has been developed to detect chemicals with the potential to disrupt reproductive endocrine function controlled by estrogen- and androgen-mediated pathways. The objective of this study was to use the assay to characterize responses of fathead Minnow reproductive endocrinology and physiology to the mammalian antiandrogen, flutamide. Male and female fish were exposed to nominal (target) concentrations of 50 and 500 μg flutamide/l for 21-days, following which plasma steroid and vitellogenin concentrations were determined and gonadal morphology assessed. Fecundity of the fish was significantly reduced by exposure to a measured test concentration of 651 μg flutamide/l. In addition, embryo hatch was significantly reduced at this concentration. Qualitative histological assessment of ovaries from females exposed to flutamide indicated a decrease in mature oocytes and an increase in atretic follicles. Testes of males exposed to flutamide exhibited spermatocyte degeneration and necrosis. Concentration-dependent increases in plasma testosterone and vitellogenin concentrations were observed in the females. Flutamide also altered reproductive endocrinology of male fathead Minnows. Males exposed to 651 μg flutamide/l exhibited elevated concentrations of β-estradiol and vitellogenin. In summary, the results of this study with the fathead Minnow demonstrate that flutamide affects reproductive endocrine function in fish and that the type of hormonal pattern and histopathology effects observed are consistent with an antiandrogenic mode-of-action. Consequently, our findings suggest that the 21-day reproduction assay utilizing fathead Minnows is a sensitive short-term screening method for the detection of endocrine-disrupting chemicals, including antiandrogens.
Michael D Kahl - One of the best experts on this subject based on the ideXlab platform.
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ketoconazole in the fathead Minnow pimephales promelas reproductive toxicity and biological compensation
Environmental Toxicology and Chemistry, 2007Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Lindsey S Blake, Katie J Greene, Rodney D Johnson, Daniel L VilleneuveAbstract:: Ketoconazole (KTC) is a model pharmaceutical representing imidazole and triazole pesticides, which inhibit fungal growth through blocking a cytochrome P450 (CYP)-mediated step in ergosterol biosynthesis. Several of these fungicides have been shown to be reversible inhibitors of CYPs in vertebrates (primarily mammals), including CYP isoforms involved in the pathway that converts cholesterol to active sex steroids. In these studies, we assessed the effects of KTC on aspects of steroidogenesis and reproductive function in the fathead Minnow (Pimephales promelas). Exposure of spawning adults to the fungicide for 21 d significantly decreased egg production at a water concentration as low as 25 microg/L. Despite evidence of reduced ex vivo testosterone production by gonads from KTC-exposed fathead Minnows, circulating plasma concentrations of sex steroids (testosterone, 17beta-estradiol) were not affected. Exposure to KTC caused an increase in the gonadosomatic index in both sexes and, in males, the fungicide caused a marked proliferation of interstitial (Leydig) cells. In addition, mRNA transcripts for two key steroidogenic enzymes, cytochrome P450 side-chain cleavage (CYP11A) and cytochrome P450 c17alpha hydroxylase/17,20 lyase (CYP17), were elevated by exposure to KTC. Both the changes in transcript levels and proliferation of gonad tissue represent potential adaptive or compensatory responses to impaired steroidogenic capacity. Overall our data indicate that, although KTC does adversely affect steroidogenesis and reproduction in the fathead Minnow, the fish can compensate to some degree to mitigate effects of the fungicide. This has important implications for the interpretation of data from tests with endocrine-active chemicals.
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linkage of biochemical responses to population level effects a case study with vitellogenin in the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2007Co-Authors: David H Miller, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Daniel L Villeneuve, Elizabeth J Durhan, Gerald T. AnkleyAbstract:A challenge in the field of ecotoxicology is the linkage of alterations at molecular and biochemical levels of organization to adverse outcomes in individuals and populations. In the present study, a predictive relationship between plasma vitellogenin (VTG) concentration and fecundity in female fathead Minnows (Pimephales promelas) was derived from 21-d laboratory toxicity tests with five chemicals (17β-trenbolone, 17α-trenbolone, prochloraz, fenarimol, and fadrozole) that inhibit VTG production through different mechanisms. Because VTG is key to egg production in female oviparous animals, changes in the lipoprotein could, theoretically, serve as an indicator of reproductive success. Regression of fecundity versus VTG concentration from the various studies yielded a highly significant linear model (fecundity = −0.042 + 0.95-VTG, p < 0.01, r2 = 0.88). This relationship was integrated into a population model to translate changes in VTG concentrations of female fathead Minnows to alterations in population growth. The model predicted relatively profound effects on population size offish experiencing moderate decreases in vitellogenesis. For example, a fathead Minnow population at a carrying capacity exposed to a chemical stressor that causes a 25% decrease in VTG concentration in females from baseline values would exhibit a 34.6% projected decrease in size after two years of exposure and reach an equilibrium population size that was only 30.2% of the preexposed population. Overall, the current study provides an example of how changes in a biomarker (VTG concentration) can be quantitatively translated into adverse effects at the individual and population levels.
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reproductive and developmental toxicity and bioconcentration of perfluorooctanesulfonate in a partial life cycle test with the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2005Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Richard L Leino, Douglas W Kuehl, Ann Linnum, Dan A VilleneuveAbstract:Perfluorooctanesulfonate (PFOS) is a widespread environmental contaminant emanating from the production and/or metabolism of fluorinated chemicals with a variety of applications. The goal of this work was to assess the toxicity and bioconcentration of PFOS in the fathead Minnow (Pimephales promelas). Sexually mature fish were exposed via the water for 21 d to 0 (control), 0.03, 0.1, 0.3, or 1 mg PFOS/L, and effects on reproductive capacity and endocrinology were assessed. To determine possible developmental effects, a subset of embryos from parental exposures at each test concentration were held for an additional 24 d in the same PFOS treatments. A concentration of 1 mg PFOS/L was lethal to adults within two weeks. The 21-d 50% effect concentration (95% confidence interval) for effects on fecundity of the fish was 0.23 (0.19–0.25) mg PFOS/L. Exposure to PFOS caused various histopathological alterations, most prominently in ovaries of adult females. Adult males exposed to 0.3 mg PFOS/L for 21 d exhibited decreased aromatase activity and elevated concentrations of plasma 11-ketotestosterone and testosterone. No significant adverse effects on survival or growth were observed in developing fathead Minnows held for 24 d at PFOS concentrations up to 0.3 mg/L. Adult fathead Minnows readily accumulated PFOS from the water. The largest concentrations of PFOS were in blood, followed by liver and then gonad; for all tissues, females accumulated higher concentrations than males. Water and tissue concentrations of PFOS associated with effects in this study exceeded those reported for samples collected from the field by two to three orders of magnitude, suggesting that the current risk of PFOS on aspects offish reproduction and development assessed in this study would be small.
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characterization of responses to the antiandrogen flutamide in a short term reproduction assay with the fathead Minnow
Aquatic Toxicology, 2004Co-Authors: Kathleen M Jensen, Joseph J. Korte, Michael D Kahl, Elizabeth A Makynen, Richard L Leino, Brian C Butterworth, Gerald T. AnkleyAbstract:Abstract A short-term reproduction assay with the fathead Minnow (Pimephales promelas) has been developed to detect chemicals with the potential to disrupt reproductive endocrine function controlled by estrogen- and androgen-mediated pathways. The objective of this study was to use the assay to characterize responses of fathead Minnow reproductive endocrinology and physiology to the mammalian antiandrogen, flutamide. Male and female fish were exposed to nominal (target) concentrations of 50 and 500 μg flutamide/l for 21-days, following which plasma steroid and vitellogenin concentrations were determined and gonadal morphology assessed. Fecundity of the fish was significantly reduced by exposure to a measured test concentration of 651 μg flutamide/l. In addition, embryo hatch was significantly reduced at this concentration. Qualitative histological assessment of ovaries from females exposed to flutamide indicated a decrease in mature oocytes and an increase in atretic follicles. Testes of males exposed to flutamide exhibited spermatocyte degeneration and necrosis. Concentration-dependent increases in plasma testosterone and vitellogenin concentrations were observed in the females. Flutamide also altered reproductive endocrinology of male fathead Minnows. Males exposed to 651 μg flutamide/l exhibited elevated concentrations of β-estradiol and vitellogenin. In summary, the results of this study with the fathead Minnow demonstrate that flutamide affects reproductive endocrine function in fish and that the type of hormonal pattern and histopathology effects observed are consistent with an antiandrogenic mode-of-action. Consequently, our findings suggest that the 21-day reproduction assay utilizing fathead Minnows is a sensitive short-term screening method for the detection of endocrine-disrupting chemicals, including antiandrogens.
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effects of the androgenic growth promoter 17 β trenbolone on fecundity and reproductive endocrinology of the fathead Minnow
Environmental Toxicology and Chemistry, 2003Co-Authors: Gerald T. Ankley, Joseph J. Korte, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Richard L Leino, Michael W Hornung, Tala R Henry, Jeffrey S Denny, Vickie S WilsonAbstract:Trenbolone acetate is a synthetic steroid that is extensively used in the United States as a growth promoter in beef cattle. The acetate is administered to livestock via slow-release implants; some is converted by the animal to 17-β-trenbolone, a relatively potent androgen receptor agonist in mammalian systems. Recent studies indicate that excreted 17-β-trenbolone is comparatively stable in animal waste, suggesting the potential for exposure to aquatic animals via direct discharge, runoff, or both. However, little is known concerning the toxicity of trenbolone to fish. Our goal was to assess the effects of 17-β-trenbolone on reproductive endocrinology of the fathead Minnow (Pimephales promelas). An in vitro competitive binding study with the fathead Minnow androgen receptor demonstrated that 17-β-trenbolone had a higher affinity for the receptor than that of the endogenous ligand, testosterone. Male and female fish were exposed for 21 d to nominal (target) concentrations of 17-β-trenbolone ranging from 0.005 to 50 μg/L. Fecundity of the fish was significantly reduced by exposure to measured test concentrations ≥ 0.027 μg/ L. The 17-β-trenbolone was clearly androgenic in vivo at these concentrations, as evidenced by the de novo production in females of dorsal (nuptial) tubercles, structures normally present only on the heads of mature males. Plasma steroid (testosterone and β-estradiol) and vitellogenin concentrations in the females all were significantly reduced by exposure to 17-β-trenbolone. The 17-β-trenbolone also altered reproductive physiology of male fathead Minnows, albeit at concentrations much higher than those producing effects in females. Males exposed to 17-β-trenbolone at 41 μg/L (measured) exhibited decreased plasma concentrations of 11-ketotestosterone and increased concentrations of β-estradiol and vitellogenin. Overall, our studies indicate that 17-β-trenbolone is a potent androgen and reproductive toxicant in fish. Given the widespread use of trenbolone acetate as a growth promoter, and relative stability of its metabolites in animal wastes, further studies are warranted to assess potential ecological risk.
Richard L Leino - One of the best experts on this subject based on the ideXlab platform.
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reproductive and developmental toxicity and bioconcentration of perfluorooctanesulfonate in a partial life cycle test with the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2005Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Richard L Leino, Douglas W Kuehl, Ann Linnum, Dan A VilleneuveAbstract:Perfluorooctanesulfonate (PFOS) is a widespread environmental contaminant emanating from the production and/or metabolism of fluorinated chemicals with a variety of applications. The goal of this work was to assess the toxicity and bioconcentration of PFOS in the fathead Minnow (Pimephales promelas). Sexually mature fish were exposed via the water for 21 d to 0 (control), 0.03, 0.1, 0.3, or 1 mg PFOS/L, and effects on reproductive capacity and endocrinology were assessed. To determine possible developmental effects, a subset of embryos from parental exposures at each test concentration were held for an additional 24 d in the same PFOS treatments. A concentration of 1 mg PFOS/L was lethal to adults within two weeks. The 21-d 50% effect concentration (95% confidence interval) for effects on fecundity of the fish was 0.23 (0.19–0.25) mg PFOS/L. Exposure to PFOS caused various histopathological alterations, most prominently in ovaries of adult females. Adult males exposed to 0.3 mg PFOS/L for 21 d exhibited decreased aromatase activity and elevated concentrations of plasma 11-ketotestosterone and testosterone. No significant adverse effects on survival or growth were observed in developing fathead Minnows held for 24 d at PFOS concentrations up to 0.3 mg/L. Adult fathead Minnows readily accumulated PFOS from the water. The largest concentrations of PFOS were in blood, followed by liver and then gonad; for all tissues, females accumulated higher concentrations than males. Water and tissue concentrations of PFOS associated with effects in this study exceeded those reported for samples collected from the field by two to three orders of magnitude, suggesting that the current risk of PFOS on aspects offish reproduction and development assessed in this study would be small.
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characterization of responses to the antiandrogen flutamide in a short term reproduction assay with the fathead Minnow
Aquatic Toxicology, 2004Co-Authors: Kathleen M Jensen, Joseph J. Korte, Michael D Kahl, Elizabeth A Makynen, Richard L Leino, Brian C Butterworth, Gerald T. AnkleyAbstract:Abstract A short-term reproduction assay with the fathead Minnow (Pimephales promelas) has been developed to detect chemicals with the potential to disrupt reproductive endocrine function controlled by estrogen- and androgen-mediated pathways. The objective of this study was to use the assay to characterize responses of fathead Minnow reproductive endocrinology and physiology to the mammalian antiandrogen, flutamide. Male and female fish were exposed to nominal (target) concentrations of 50 and 500 μg flutamide/l for 21-days, following which plasma steroid and vitellogenin concentrations were determined and gonadal morphology assessed. Fecundity of the fish was significantly reduced by exposure to a measured test concentration of 651 μg flutamide/l. In addition, embryo hatch was significantly reduced at this concentration. Qualitative histological assessment of ovaries from females exposed to flutamide indicated a decrease in mature oocytes and an increase in atretic follicles. Testes of males exposed to flutamide exhibited spermatocyte degeneration and necrosis. Concentration-dependent increases in plasma testosterone and vitellogenin concentrations were observed in the females. Flutamide also altered reproductive endocrinology of male fathead Minnows. Males exposed to 651 μg flutamide/l exhibited elevated concentrations of β-estradiol and vitellogenin. In summary, the results of this study with the fathead Minnow demonstrate that flutamide affects reproductive endocrine function in fish and that the type of hormonal pattern and histopathology effects observed are consistent with an antiandrogenic mode-of-action. Consequently, our findings suggest that the 21-day reproduction assay utilizing fathead Minnows is a sensitive short-term screening method for the detection of endocrine-disrupting chemicals, including antiandrogens.
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effects of the androgenic growth promoter 17 β trenbolone on fecundity and reproductive endocrinology of the fathead Minnow
Environmental Toxicology and Chemistry, 2003Co-Authors: Gerald T. Ankley, Joseph J. Korte, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Richard L Leino, Michael W Hornung, Tala R Henry, Jeffrey S Denny, Vickie S WilsonAbstract:Trenbolone acetate is a synthetic steroid that is extensively used in the United States as a growth promoter in beef cattle. The acetate is administered to livestock via slow-release implants; some is converted by the animal to 17-β-trenbolone, a relatively potent androgen receptor agonist in mammalian systems. Recent studies indicate that excreted 17-β-trenbolone is comparatively stable in animal waste, suggesting the potential for exposure to aquatic animals via direct discharge, runoff, or both. However, little is known concerning the toxicity of trenbolone to fish. Our goal was to assess the effects of 17-β-trenbolone on reproductive endocrinology of the fathead Minnow (Pimephales promelas). An in vitro competitive binding study with the fathead Minnow androgen receptor demonstrated that 17-β-trenbolone had a higher affinity for the receptor than that of the endogenous ligand, testosterone. Male and female fish were exposed for 21 d to nominal (target) concentrations of 17-β-trenbolone ranging from 0.005 to 50 μg/L. Fecundity of the fish was significantly reduced by exposure to measured test concentrations ≥ 0.027 μg/ L. The 17-β-trenbolone was clearly androgenic in vivo at these concentrations, as evidenced by the de novo production in females of dorsal (nuptial) tubercles, structures normally present only on the heads of mature males. Plasma steroid (testosterone and β-estradiol) and vitellogenin concentrations in the females all were significantly reduced by exposure to 17-β-trenbolone. The 17-β-trenbolone also altered reproductive physiology of male fathead Minnows, albeit at concentrations much higher than those producing effects in females. Males exposed to 17-β-trenbolone at 41 μg/L (measured) exhibited decreased plasma concentrations of 11-ketotestosterone and increased concentrations of β-estradiol and vitellogenin. Overall, our studies indicate that 17-β-trenbolone is a potent androgen and reproductive toxicant in fish. Given the widespread use of trenbolone acetate as a growth promoter, and relative stability of its metabolites in animal wastes, further studies are warranted to assess potential ecological risk.
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evaluation of the aromatase inhibitor fadrozole in a short term reproduction assay with the fathead Minnow pimephales promelas
Toxicological Sciences, 2002Co-Authors: Gerald T. Ankley, Joseph J. Korte, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Michael W Hornung, Richard L LeinoAbstract:Cytochrome P450 aromatase (CYP19) is a key enzyme in vertebrate steroidogenesis, catalyzing the conversion of C19 androgens to C18 estrogens such as b-estradiol (E2). The objective of this study was to assess effects of the CYP19 inhibitor fadrozole on fathead Minnow (Pimephales promelas) reproductive endocrinology and physiology in a short-term reproduction assay proposed for identifying specific classes of endocrine-disrupting chemicals. A concentration-dependent reduction in fecundity was observed in fish exposed for 21 days to water concentrations of fadrozole ranging from 2 to 50 mg/l. Consistent with the expected mechanism of action, there was a significant inhibition of brain aromatase activity in both male and female fathead Minnows exposed to fadrozole. In females, this inhibition was accompanied by a concentration-dependent decrease in plasma E2 and vitellogenin concentrations; the latter observation is consistent with the fact that activation of the estrogen receptor by E2 initiates hepatic vitellogenin production in oviparous vertebrates. Histological assessment of ovaries from females exposed to fadrozole indicated a decrease in mature oocytes and an increase in preovulatory atretic follicles. Exposure of male fathead Minnows to fadrozole significantly increased plasma concentrations of the androgens testosterone (T) and 11-ketotestosterone (KT) and resulted in a marked accumulation of sperm in the testes. Results of this study indicate that the proposed fathead Minnow assay should effectively identify test chemicals as potential aromatase inhibitors, both in the context of their reproductive toxicity and the specific mechanism of action. These results also should be of utility in assessing the potential ecological risk of CYP19 inhibitors, in particular in the context of relating alterations in subcellular indicators of endocrine function (changes in steroids, proteins) to adverse consequences in the whole organism.
Elizabeth A Makynen - One of the best experts on this subject based on the ideXlab platform.
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comparison of fathead Minnow ovary explant and h295r cell based steroidogenesis assays for identifying endocrine active chemicals
Ecotoxicology and Environmental Safety, 2007Co-Authors: Daniel L Villeneuve, Gerald T. Ankley, Elizabeth A Makynen, Lindsey S Blake, Katie J Greene, Eric Higley, John L Newsted, John P GiesyAbstract:An in vitro steroidogenesis assay using H295R human adenocarcinoma cells has been suggested as a possible alternative to gonad explant assays for use as a Tier I screening assay to detect endocrine active chemicals capable of modulating steroid hormone synthesis. This study is one of the first to investigate the utility of the H295R assay for predicting effects and/or understanding mechanisms of action across species and tissues. Six chemicals, including one selective aromatase inhibitor (fadrozole), four fungicides (fenarimol, ketoconazole, prochloraz, and vinclozolin), and one herbicide (prometon), were tested in both the H295R steroidogenesis assay, and an in vitro steroidogenesis assay using fathead Minnow ovary explants. All six chemicals caused significant alterations in 17β-estradiol (E2) and/or testosterone (T) production in vitro. Effects of ketoconazole, prochloraz, and prometon were similar in both assays. However, there were differences in the profile of responses for T for fadrozole and fenarimol, and for T and E2 for vinclozolin. In terms of sensitivity, steroid production in the H295R assay was most sensitive for detecting the effects of fadrozole, fenarimol, and prochloraz, but was less sensitive than the fathead Minnow ovary explant assay to the effects of ketoconazole and vinclozolin. The H295R assay was consistently less variable (among replicates) than the fathead Minnow ovary explant assay. However, the ovary explant assay was more predictive of in vivo effects of the six chemicals on fathead Minnows than the H295R system. Further characterization of autoregulatory capacities, interaction of steroid-hormone receptor pathways with steroidogenesis, and metabolic capabilities of each system are needed for either system to provide clear and informative insights regarding a chemical's mechanism of action. Overall, however, results of this study suggest that both the H295R and fathead Minnow ovary explant assays have utility for identifying endocrine-active chemicals in screening-type applications.
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ketoconazole in the fathead Minnow pimephales promelas reproductive toxicity and biological compensation
Environmental Toxicology and Chemistry, 2007Co-Authors: Gerald T. Ankley, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Lindsey S Blake, Katie J Greene, Rodney D Johnson, Daniel L VilleneuveAbstract:: Ketoconazole (KTC) is a model pharmaceutical representing imidazole and triazole pesticides, which inhibit fungal growth through blocking a cytochrome P450 (CYP)-mediated step in ergosterol biosynthesis. Several of these fungicides have been shown to be reversible inhibitors of CYPs in vertebrates (primarily mammals), including CYP isoforms involved in the pathway that converts cholesterol to active sex steroids. In these studies, we assessed the effects of KTC on aspects of steroidogenesis and reproductive function in the fathead Minnow (Pimephales promelas). Exposure of spawning adults to the fungicide for 21 d significantly decreased egg production at a water concentration as low as 25 microg/L. Despite evidence of reduced ex vivo testosterone production by gonads from KTC-exposed fathead Minnows, circulating plasma concentrations of sex steroids (testosterone, 17beta-estradiol) were not affected. Exposure to KTC caused an increase in the gonadosomatic index in both sexes and, in males, the fungicide caused a marked proliferation of interstitial (Leydig) cells. In addition, mRNA transcripts for two key steroidogenic enzymes, cytochrome P450 side-chain cleavage (CYP11A) and cytochrome P450 c17alpha hydroxylase/17,20 lyase (CYP17), were elevated by exposure to KTC. Both the changes in transcript levels and proliferation of gonad tissue represent potential adaptive or compensatory responses to impaired steroidogenic capacity. Overall our data indicate that, although KTC does adversely affect steroidogenesis and reproduction in the fathead Minnow, the fish can compensate to some degree to mitigate effects of the fungicide. This has important implications for the interpretation of data from tests with endocrine-active chemicals.
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linkage of biochemical responses to population level effects a case study with vitellogenin in the fathead Minnow pimephales promelas
Environmental Toxicology and Chemistry, 2007Co-Authors: David H Miller, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Daniel L Villeneuve, Elizabeth J Durhan, Gerald T. AnkleyAbstract:A challenge in the field of ecotoxicology is the linkage of alterations at molecular and biochemical levels of organization to adverse outcomes in individuals and populations. In the present study, a predictive relationship between plasma vitellogenin (VTG) concentration and fecundity in female fathead Minnows (Pimephales promelas) was derived from 21-d laboratory toxicity tests with five chemicals (17β-trenbolone, 17α-trenbolone, prochloraz, fenarimol, and fadrozole) that inhibit VTG production through different mechanisms. Because VTG is key to egg production in female oviparous animals, changes in the lipoprotein could, theoretically, serve as an indicator of reproductive success. Regression of fecundity versus VTG concentration from the various studies yielded a highly significant linear model (fecundity = −0.042 + 0.95-VTG, p < 0.01, r2 = 0.88). This relationship was integrated into a population model to translate changes in VTG concentrations of female fathead Minnows to alterations in population growth. The model predicted relatively profound effects on population size offish experiencing moderate decreases in vitellogenesis. For example, a fathead Minnow population at a carrying capacity exposed to a chemical stressor that causes a 25% decrease in VTG concentration in females from baseline values would exhibit a 34.6% projected decrease in size after two years of exposure and reach an equilibrium population size that was only 30.2% of the preexposed population. Overall, the current study provides an example of how changes in a biomarker (VTG concentration) can be quantitatively translated into adverse effects at the individual and population levels.
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characterization of responses to the antiandrogen flutamide in a short term reproduction assay with the fathead Minnow
Aquatic Toxicology, 2004Co-Authors: Kathleen M Jensen, Joseph J. Korte, Michael D Kahl, Elizabeth A Makynen, Richard L Leino, Brian C Butterworth, Gerald T. AnkleyAbstract:Abstract A short-term reproduction assay with the fathead Minnow (Pimephales promelas) has been developed to detect chemicals with the potential to disrupt reproductive endocrine function controlled by estrogen- and androgen-mediated pathways. The objective of this study was to use the assay to characterize responses of fathead Minnow reproductive endocrinology and physiology to the mammalian antiandrogen, flutamide. Male and female fish were exposed to nominal (target) concentrations of 50 and 500 μg flutamide/l for 21-days, following which plasma steroid and vitellogenin concentrations were determined and gonadal morphology assessed. Fecundity of the fish was significantly reduced by exposure to a measured test concentration of 651 μg flutamide/l. In addition, embryo hatch was significantly reduced at this concentration. Qualitative histological assessment of ovaries from females exposed to flutamide indicated a decrease in mature oocytes and an increase in atretic follicles. Testes of males exposed to flutamide exhibited spermatocyte degeneration and necrosis. Concentration-dependent increases in plasma testosterone and vitellogenin concentrations were observed in the females. Flutamide also altered reproductive endocrinology of male fathead Minnows. Males exposed to 651 μg flutamide/l exhibited elevated concentrations of β-estradiol and vitellogenin. In summary, the results of this study with the fathead Minnow demonstrate that flutamide affects reproductive endocrine function in fish and that the type of hormonal pattern and histopathology effects observed are consistent with an antiandrogenic mode-of-action. Consequently, our findings suggest that the 21-day reproduction assay utilizing fathead Minnows is a sensitive short-term screening method for the detection of endocrine-disrupting chemicals, including antiandrogens.
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effects of the androgenic growth promoter 17 β trenbolone on fecundity and reproductive endocrinology of the fathead Minnow
Environmental Toxicology and Chemistry, 2003Co-Authors: Gerald T. Ankley, Joseph J. Korte, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Richard L Leino, Michael W Hornung, Tala R Henry, Jeffrey S Denny, Vickie S WilsonAbstract:Trenbolone acetate is a synthetic steroid that is extensively used in the United States as a growth promoter in beef cattle. The acetate is administered to livestock via slow-release implants; some is converted by the animal to 17-β-trenbolone, a relatively potent androgen receptor agonist in mammalian systems. Recent studies indicate that excreted 17-β-trenbolone is comparatively stable in animal waste, suggesting the potential for exposure to aquatic animals via direct discharge, runoff, or both. However, little is known concerning the toxicity of trenbolone to fish. Our goal was to assess the effects of 17-β-trenbolone on reproductive endocrinology of the fathead Minnow (Pimephales promelas). An in vitro competitive binding study with the fathead Minnow androgen receptor demonstrated that 17-β-trenbolone had a higher affinity for the receptor than that of the endogenous ligand, testosterone. Male and female fish were exposed for 21 d to nominal (target) concentrations of 17-β-trenbolone ranging from 0.005 to 50 μg/L. Fecundity of the fish was significantly reduced by exposure to measured test concentrations ≥ 0.027 μg/ L. The 17-β-trenbolone was clearly androgenic in vivo at these concentrations, as evidenced by the de novo production in females of dorsal (nuptial) tubercles, structures normally present only on the heads of mature males. Plasma steroid (testosterone and β-estradiol) and vitellogenin concentrations in the females all were significantly reduced by exposure to 17-β-trenbolone. The 17-β-trenbolone also altered reproductive physiology of male fathead Minnows, albeit at concentrations much higher than those producing effects in females. Males exposed to 17-β-trenbolone at 41 μg/L (measured) exhibited decreased plasma concentrations of 11-ketotestosterone and increased concentrations of β-estradiol and vitellogenin. Overall, our studies indicate that 17-β-trenbolone is a potent androgen and reproductive toxicant in fish. Given the widespread use of trenbolone acetate as a growth promoter, and relative stability of its metabolites in animal wastes, further studies are warranted to assess potential ecological risk.
