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Moshe Finel - One of the best experts on this subject based on the ideXlab platform.
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human efflux transport of testosterone epitestosterone and other androgen glucuronides
The Journal of Steroid Biochemistry and Molecular Biology, 2020Co-Authors: Erkka Jarvinen, Heidi Kidron, Moshe FinelAbstract:Abstract Several drug-metabolizing enzymes are known to control androgen homeostasis in humans. UDP-glucuronosyltransferases convert androgens to glucuronide conjugates in the liver and intestine, which enables subsequent elimination of these conjugated androgens via urine. The most important androgen is testosterone, while others are the testosterone metabolites androsterone and Etiocholanolone, and the testosterone precursor dehydroepiandrosterone. Epitestosterone is another endogenous androgen, which is included as a crucial marker in urine doping tests. Since glucuronide conjugates are hydrophilic, efflux transporters mediate their excretion from tissues. In this study, we employed the membrane vesicle assay to identify the efflux transporters for glucuronides of androsterone, dehydroepiandrosterone, epitestosterone, Etiocholanolone and testosterone. The human hepatic and intestinal transporters MRP2 (ABCC2), MRP3 (ABCC3), MRP4 (ABCC4), BCRP (ABCG2) and MDR1 (ABCB1) were studied in vitro. Of these transporters, only MRP2 and MRP3 transported the androgen glucuronides investigated. In kinetic analyses, MRP3 transported glucuronides of androsterone, epitestosterone and Etiocholanolone at low Km values, between 0.4 and 4 μM, while the Km values for glucuronides of testosterone and dehydroepiandrosterone were 14 and 51 μM, respectively. MRP2 transported the glucuronides at lower affinity, as indicated by Km values over 100 μM. Interestingly, the MRP2-mediated transport of androsterone and epitestosterone glucuronides was best described by sigmoidal kinetics. The inability of BCRP to transport any of the androgen glucuronides investigated is drastically different from its highly active transport of several estrogen conjugates. Our results explain the transporter-mediated disposition of androgen glucuronides in humans, and shed light on differences between the human efflux transporters MRP2, MRP3, MRP4, BCRP and MDR1.
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Glucuronidation of the steroid enantiomers ent-17β-estradiol, ent-androsterone and ent-Etiocholanolone by the human UDP-glucuronosyltransferases.
The Journal of steroid biochemistry and molecular biology, 2011Co-Authors: Nina Sneitz, Douglas F Covey, Kathiresan Krishnan, Moshe FinelAbstract:Steroids enantiomers are interesting compounds for detailed exploration of drug metabolizing enzymes, such as the UDP-glucuronosyltransferases (UGTs). We have now studied the glucuronidation of the enantiomers of estradiol, androsterone and Etiocholanolone by the 19 human UGTs of subfamilies 1A, 2A and 2B. The results reveal that the pattern of human UGTs of subfamily 2B that glucuronidate ent-17β-estradiol, particularly 2B15 and 2B17, resembles the glucuronidation of epiestradiol (17α-estradiol) rather than 17β-estradiol, the main physiological estrogen. The UGTs of subfamilies 1A and 2A exhibit higher degree of regioselectivity than enantioselectivity in the conjugation of these estradiols, regardless of whether the activity is primarily toward the non-chiral site, 3-OH (UGT1A1, UGT1A3, UGT1A7, UGT1A8 and, above all, UGT1A10), or the 17-OH (UGT1A4). In the cases of Etiocholanolone and androsterone, glucuronidation of the ent-androgens, like the conjugation of the natural androgens, is mainly catalyzed by UGTs of subfamilies 2A and 2B. Nevertheless, the glucuronidation of ent-Etiocholanolone and ent-androsterone by both UGT2B7 and UGT2B17 differs considerably from their respective activity toward the corresponding endogenous androgens, whereas UGT2A1-catalyzed conjugation is much less affected by the stereochemistry differences. Kinetic analyses reveal that the K(m) value of UGT2A1 for ent-estradiol is much higher than the corresponding value in the other two high activity enzymes, UGT1A10 and UGT2B7. Taken together, the results highlight large enantioselectivity differences between individual UGTs, particularly those of subfamily 2B.
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UDP-Glucuronosyltransferases in Conjugation of 5α- and 5β-Androstane Steroids
Drug metabolism and disposition: the biological fate of chemicals, 2009Co-Authors: Taina Sten, Mika Kurkela, Tiia Kuuranne, Antti Leinonen, Moshe FinelAbstract:We have examined the glucuronidation of androsterone (5alpha-androstane-3alpha-ol-17-one), Etiocholanolone (5beta-androstane-3alpha-ol-17-one), 5alpha-androstane-3alpha-,17beta-diol (5alpha-diol), and 5beta-androstane-3alpha-, 17beta-diol (5beta-diol) by 19 recombinant human UDP-glucuronosyltransferases (UGTs). The results reveal large differences in stereo- and regioselectivity between UGT2B7, UGT2B15, and UGT2B17. UGT2B7 conjugated all four androgens at the 3-OH but not at the 17-OH that is available in both diols. UGT2B7 exhibited a higher glucuronidation rate toward the steroids with a flat backbone, androsterone and 5alpha-diol, compared with Etiocholanolone and 5beta-diol, which have a bent backbone. UGT2B17 readily glucuronidated androsterone and, particularly, Etiocholanolone at the 3-OH, but in the two diols it exhibited high preference for the 17-OH and low glucuronidation rate at the 3-OH. UGT2B15 did not glucuronidate any of the studied four androgens at the 3-OH, but it did conjugate both diols at the 17-OH, with a clear preference for 5alpha-diol. Of the UGT1A subfamily, only UGT1A4 catalyzed the glucuronidation of androsterone and 5alpha-diol at measurable rates, even if low. UGT2A1 and UGT2A2 glucuronidated most compounds in this study, but mostly at rather low rates. An exception was the glucuronidation of Etiocholanolone by UGT2A1 that revealed a very low substrate affinity in combination with very high V(max) value. The results shed new light on the substrate selectivity of individual UGTs in steroid glucuronidation. In addition they bear implications for doping analyses and its dependence of genetic polymorphism because testosterone is a precursor in the biosynthesis of these four androgens, whereas the contribution of UGT2B17 to their glucuronidation varies greatly.
Gustav Akk - One of the best experts on this subject based on the ideXlab platform.
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natural and enantiomeric Etiocholanolone interact with distinct sites on the rat α1β2γ2l gabaa receptor
Molecular Pharmacology, 2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat alpha1beta2gamma2L GABA(A) receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABA(A) receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing potentiation. At a low GABA concentration (0.5 microM,
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Natural and Enantiomeric Etiocholanolone Interact with Distinct Sites on the Rat α1β2γ2L GABAA Receptor
Molecular pharmacology, 2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat alpha1beta2gamma2L GABA(A) receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABA(A) receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing potentiation. At a low GABA concentration (0.5 microM,
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Natural and enantiomeric Etiocholanolone interact with distinct sites on the rat α1β2γ2L GABAA receptor
2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat 122L GABAA receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABAA receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing poten-tiation. At a low GABA concentration (0.5 M, EC5), the presence of 10 M ent-Etiocholanolone potentiates whole-cell currents by almost 30-fold, whereas 10 M Etiocholanolone merely doubles the peak response. At higher GABA concentra-tion (5 M, EC25), the potentiation curve for ent-etiochol-anolone is positioned at lower concentrations than that fo
Ryan T Paitz - One of the best experts on this subject based on the ideXlab platform.
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Characterizing the timing of yolk testosterone metabolism and the effects of Etiocholanolone on development in avian eggs.
The Journal of experimental biology, 2020Co-Authors: Nicole A Campbell, Rachel Angles, Rachel M Bowden, Joseph M Casto, Ryan T PaitzAbstract:Maternal transfer of steroids to eggs can elicit permanent effects on offspring phenotype. Although testosterone was thought to be a key mediator of maternal effects in birds, we now know that vertebrate embryos actively regulate their exposure to maternal testosterone through steroid metabolism, suggesting testosterone metabolites, not testosterone, may elicit the observed phenotypic effects. To address the role steroid metabolism plays in mediating yolk testosterone effects, we used European starling (Sturnus vulgaris) eggs to characterize the timing of testosterone metabolism and determine whether Etiocholanolone, a prominent metabolite of testosterone in avian embryos, is capable of affecting early embryonic development. Tritiated testosterone was injected into freshly laid eggs to characterize steroid movement and metabolism during early development. Varying levels of Etiocholanolone were also injected into eggs, with incubation for either 3 or 5 days, to test whether Etiocholanolone influences the early growth of embryonic tissues. The conversion of testosterone to Etiocholanolone was initiated within 12 h of injection, but the increase in Etiocholanolone was transient, indicating that Etiocholanolone is also subject to metabolism, and that exposure to maternal Etiocholanolone is limited to a short period during early development. Exogenous Etiocholanolone manipulation had no significant effect on the growth rate of the embryos or extra-embryonic membranes early in development. Thus, the conversion of testosterone to Etiocholanolone may be an inactivation pathway that buffers the embryo from maternal steroids, with any effects of yolk testosterone resulting from testosterone that escapes metabolism; alternatively, Etiocholanolone may influence processes other than growth or take additional time to manifest.
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Characterizing the timing of yolk testosterone metabolism and the effects of Etiocholanolone on development in avian eggs.
The Journal of Experimental Biology, 2020Co-Authors: Nicole A Campbell, Rachel Angles, Rachel M Bowden, Joseph M Casto, Ryan T PaitzAbstract:Maternal transfer of steroids to eggs can elicit permanent effects on offspring phenotype. Although testosterone was thought to be a key mediator of maternal effects in birds, we now know that vertebrate embryos actively regulate their exposure to maternal testosterone through steroid metabolism, suggesting testosterone metabolites, not testosterone, may elicit the observed phenotypic effects. To address the role steroid metabolism plays in mediating yolk testosterone effects, we used European starling (Sturnus vulgaris) eggs to characterize the timing of testosterone metabolism and determine whether Etiocholanolone, a prominent metabolite of testosterone in avian embryos, is capable of affecting early embryonic development. Tritiated testosterone was injected into freshly laid eggs to characterize steroid movement and metabolism during early development. Varying levels of Etiocholanolone were also injected into eggs and incubated for either three or five days to test whether Etiocholanolone influences the early growth of embryonic tissues. The conversion of testosterone to Etiocholanolone is initiated within 12 hours of injection, but the increase in Etiocholanolone is transient indicating that Etiocholanolone is also subject to metabolism, and that exposure to maternal Etiocholanolone is limited to a short period during early development. Exogenous Etiocholanolone manipulation had no significant effect on the growth rate of the embryos or extra-embryonic membranes early in development. Thus, the conversion of testosterone to Etiocholanolone may be an inactivation pathway that buffers the embryo from maternal steroids, with any effects of yolk testosterone resulting from testosterone that escapes metabolism; alternatively, Etiocholanolone may influence processes other than growth or take additional time to manifest.
Douglas F Covey - One of the best experts on this subject based on the ideXlab platform.
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Glucuronidation of the steroid enantiomers ent-17β-estradiol, ent-androsterone and ent-Etiocholanolone by the human UDP-glucuronosyltransferases.
The Journal of steroid biochemistry and molecular biology, 2011Co-Authors: Nina Sneitz, Douglas F Covey, Kathiresan Krishnan, Moshe FinelAbstract:Steroids enantiomers are interesting compounds for detailed exploration of drug metabolizing enzymes, such as the UDP-glucuronosyltransferases (UGTs). We have now studied the glucuronidation of the enantiomers of estradiol, androsterone and Etiocholanolone by the 19 human UGTs of subfamilies 1A, 2A and 2B. The results reveal that the pattern of human UGTs of subfamily 2B that glucuronidate ent-17β-estradiol, particularly 2B15 and 2B17, resembles the glucuronidation of epiestradiol (17α-estradiol) rather than 17β-estradiol, the main physiological estrogen. The UGTs of subfamilies 1A and 2A exhibit higher degree of regioselectivity than enantioselectivity in the conjugation of these estradiols, regardless of whether the activity is primarily toward the non-chiral site, 3-OH (UGT1A1, UGT1A3, UGT1A7, UGT1A8 and, above all, UGT1A10), or the 17-OH (UGT1A4). In the cases of Etiocholanolone and androsterone, glucuronidation of the ent-androgens, like the conjugation of the natural androgens, is mainly catalyzed by UGTs of subfamilies 2A and 2B. Nevertheless, the glucuronidation of ent-Etiocholanolone and ent-androsterone by both UGT2B7 and UGT2B17 differs considerably from their respective activity toward the corresponding endogenous androgens, whereas UGT2A1-catalyzed conjugation is much less affected by the stereochemistry differences. Kinetic analyses reveal that the K(m) value of UGT2A1 for ent-estradiol is much higher than the corresponding value in the other two high activity enzymes, UGT1A10 and UGT2B7. Taken together, the results highlight large enantioselectivity differences between individual UGTs, particularly those of subfamily 2B.
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natural and enantiomeric Etiocholanolone interact with distinct sites on the rat α1β2γ2l gabaa receptor
Molecular Pharmacology, 2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat alpha1beta2gamma2L GABA(A) receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABA(A) receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing potentiation. At a low GABA concentration (0.5 microM,
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Natural and Enantiomeric Etiocholanolone Interact with Distinct Sites on the Rat α1β2γ2L GABAA Receptor
Molecular pharmacology, 2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat alpha1beta2gamma2L GABA(A) receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABA(A) receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing potentiation. At a low GABA concentration (0.5 microM,
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Natural and enantiomeric Etiocholanolone interact with distinct sites on the rat α1β2γ2L GABAA receptor
2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat 122L GABAA receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABAA receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing poten-tiation. At a low GABA concentration (0.5 M, EC5), the presence of 10 M ent-Etiocholanolone potentiates whole-cell currents by almost 30-fold, whereas 10 M Etiocholanolone merely doubles the peak response. At higher GABA concentra-tion (5 M, EC25), the potentiation curve for ent-etiochol-anolone is positioned at lower concentrations than that fo
John Bracamontes - One of the best experts on this subject based on the ideXlab platform.
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natural and enantiomeric Etiocholanolone interact with distinct sites on the rat α1β2γ2l gabaa receptor
Molecular Pharmacology, 2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat alpha1beta2gamma2L GABA(A) receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABA(A) receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing potentiation. At a low GABA concentration (0.5 microM,
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Natural and Enantiomeric Etiocholanolone Interact with Distinct Sites on the Rat α1β2γ2L GABAA Receptor
Molecular pharmacology, 2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat alpha1beta2gamma2L GABA(A) receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABA(A) receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing potentiation. At a low GABA concentration (0.5 microM,
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Natural and enantiomeric Etiocholanolone interact with distinct sites on the rat α1β2γ2L GABAA receptor
2007Co-Authors: John Bracamontes, Bryson W Katona, Douglas F Covey, Joe Henry Steinbach, Gustav AkkAbstract:We have studied the ability of the androgen Etiocholanolone and its enantiomer (ent-Etiocholanolone) to modulate rat 122L GABAA receptor function transiently expressed in human embryonic kidney cells. Studies on steroid enantiomer pairs can yield powerful new information on the pharmacology of steroid interactions with the GABAA receptor. Both steroids enhance currents elicited by GABA, but ent-Etiocholanolone is much more powerful than Etiocholanolone at producing poten-tiation. At a low GABA concentration (0.5 M, EC5), the presence of 10 M ent-Etiocholanolone potentiates whole-cell currents by almost 30-fold, whereas 10 M Etiocholanolone merely doubles the peak response. At higher GABA concentra-tion (5 M, EC25), the potentiation curve for ent-etiochol-anolone is positioned at lower concentrations than that fo