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Juan M. Guerrero - One of the best experts on this subject based on the ideXlab platform.
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continuous light exposure modifies the nocturnal increase in rat thymus type ii Thyroxine 5 Deiodinase
Cellular and Molecular Life Sciences, 1997Co-Authors: Mohammed Soutto, Patrocinio Molinero, Juan M. GuerreroAbstract:In the present study we show that thymus type II Thyroxine Deiodinase activity exhibits a nyctohemeral profile, with basal values during the day and high values at night. This rhythmic character is dependent on neuroadrenergic input since exposure to continuous light at night completely abolished the nocturnal rise of the enzyme activity. However, treatment with isoproterenol under light exposure at night restored it.
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β- and α-adrenergic mechanisms are involved in regulating type II Thyroxine 5′-Deiodinase in rat thymus
Life sciences, 1996Co-Authors: Mohammed Soutto, Juan M. Guerrero, Patrocinio MolineroAbstract:Abstract The role of adrenergic receptors in regulation of rat thymus type II Thyroxine 5′-Deiodinase (5′-D) activity was investigated. Our results show that norepinephrine, an α- and β-adrenergic agonist elicited an increase in thymus 5′-D activity. Isoproterenol, a β-adrenergic agonist, also increased the enzyme activity, being less effective than norepinephrine. Moreover, α-adrenergic agonists, i.e., methoxamine, an α 1 -agonist, and clonidine, an α 2 -agonist, did not increase 5′-D activity. The effect of isoproterenol was potentiated by methoxamine, but the potentiating effect was observed only at doses of isoproterenol which induce submaximal activation of the enzyme. Administration of propranolol, a β-adrenergic blocker, and prazosin, an α 1 -adrenergic blocker, inhibited significantly the activation of the enzyme induced by norepinephrine. However, yohimbine, an α 2 -adrenergic blocker, had small effect These results show, in hypothyroid rats, a clear regulation by adrenergic mechanisms of 5′-D activity in the thymus, where α- and β-adrenergic receptors might be involved.
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β and α adrenergic mechanisms are involved in regulating type ii Thyroxine 5 Deiodinase in rat thymus
Life Sciences, 1995Co-Authors: Mohammed Soutto, Juan M. Guerrero, Patrocinio MolineroAbstract:Abstract The role of adrenergic receptors in regulation of rat thymus type II Thyroxine 5′-Deiodinase (5′-D) activity was investigated. Our results show that norepinephrine, an α- and β-adrenergic agonist elicited an increase in thymus 5′-D activity. Isoproterenol, a β-adrenergic agonist, also increased the enzyme activity, being less effective than norepinephrine. Moreover, α-adrenergic agonists, i.e., methoxamine, an α 1 -agonist, and clonidine, an α 2 -agonist, did not increase 5′-D activity. The effect of isoproterenol was potentiated by methoxamine, but the potentiating effect was observed only at doses of isoproterenol which induce submaximal activation of the enzyme. Administration of propranolol, a β-adrenergic blocker, and prazosin, an α 1 -adrenergic blocker, inhibited significantly the activation of the enzyme induced by norepinephrine. However, yohimbine, an α 2 -adrenergic blocker, had small effect These results show, in hypothyroid rats, a clear regulation by adrenergic mechanisms of 5′-D activity in the thymus, where α- and β-adrenergic receptors might be involved.
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type ii Thyroxine 5 Deiodinase in the rat thymus
Journal of Endocrinology, 1995Co-Authors: Patrocinio Molinero, C. Osuna, Juan M. GuerreroAbstract:In the present study we have shown type II Thyroxine 5'-deiodination (5'D) in the rat thymus. The enzyme activity was identified in crude extract homogenates by measuring the 125 I released from [3',5'- 125 I]Thyroxine which is used as a substrate of the reaction. The release of 125 I is dependent on protein tissue concentration, time, temperature and pH, and is saturable by increasing the substrate concentration, indicating its enzymatic nature. Characteristics of the enzyme activity also include a low K m (9.1 nM), its dependence on dithiothreitol, and its inhibition by iopanoic acid, but not by propylthiouracil. Experiments to investigate the cellular location of the enzyme in the thymic gland showed that the enzyme is present in both stromal cells and thymocytes. At the subcellular level, 5'D activity was associated with cellular membranes. Thyroid status appears to regulate 5'D activity in rat thymus. Hypothyroidism caused an increase in thymus 5'D activity. The K m value remained unchanged (9.1 vs 10.5 nM) during hypothyroidism, but V max increased significantly from 17.7 fmol/mg protein per h in euthyroid rats to 53.5 fmol/mg protein per h in hypothyroid rats. 5'D activity was also modulated by catecholamines through β-adrenergic receptors because isoproterenol, but not methoxamine or clonidine, could activate the enzyme. Because these characteristics define the type II iodothyronine-deiodinating pathway in other tissues, we suggest that the rat thymus also shares this pathway.
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VIP receptor-effector system in rat harderian gland and its coupling to activation of type II Thyroxine 5'-Deiodinase.
Peptides, 1995Co-Authors: Juan R. Calvo, Carmen Osuna, Maria Isabel Caraballo, David Pozo, Juan José Segura, Juan M. GuerreroAbstract:Vasoactive intestinal peptide (VIP) receptors were investigated in rat Harderian gland membranes using [125I]VIP as ligand. The receptor binding was rapid, reversible, saturable, specific, and dependent on time, temperature, and membrane concentration. At 30 degrees C, the stoichiometric data suggested the presence of two classes of VIP receptors with Kd values of 0.36 +/- 0.06 and 65.37 +/- 8.08 nM and binding capacities of 323 +/- 54 and 39,537 +/- 3100 fmol VIP/mg protein, respectively. The interaction showed a high degree of specificity, as suggested by competitive displacement experiments with several peptides structurally or not structurally related to VIP. The binding of [125I]VIP to membranes was sensitive to guanine nucleotides in a dose-dependent manner. The molecular characterization of VIP receptors was realized by chemical cross-linking; sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized membrane proteins revealed the presence of two specific [125I]VIP-protein complexes of M(r) 57 and 35 kDa as estimated in denaturing conditions. VIP stimulated adenylate cyclase activity in rat Harderian gland membranes in a dose-dependent manner. Finally, VIP stimulated in vivo the type II Thyroxine 5'-Deiodinase activity. These results demonstrate the presence of specific and functional VIP receptors in Harderian gland and suggest a role for VIP in the physiology of this gland.
Amalia Rubio - One of the best experts on this subject based on the ideXlab platform.
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effect of chronic ethanol administration on the rat pineal n acetyltransferase and Thyroxine type ii 5 Deiodinase activities
Bioscience Reports, 1993Co-Authors: Juan Ramón Jiménez, Carmen Osuna, Amalia Rubio, Juan M. GuerreroAbstract:Chronic ethanol intake resulted in a significant decrease in the rate of rat ponderal growth and an impaired nyctohemeral profile of pineal N-acetyltransferase (NAT) activity. In ethanol-treated animals, the onset of the nocturnal NAT increase is delayed by 2 hours when compared to control animals. Moreover, pineal NAT nocturnal peak was reached at 4 h (2 hours later than controls), while pineal type II Thyroxine 5′-Deiodinase (5′-D) nyctohemeral profile was not modified by ethanol administration. The effect of ethanol administration (12 weeks) on 5′-D activity in different tissues was also studied. Ethanol induced a 5′-D activity increase in hypothesis and brain frontal cortex, when compared to control animals. No change in 5′-D activity is observed in either pineal gland, Harderian gland, or brown adipose tissue. Since basal values of 5′-D activity in hypophysis or brain frontal cortex are particularly dependent on serum Thyroxine (T4) concentration, the effect of chronic ethanol administration on thyroid hormone levels was studied. Serum T4 levels in ethanol-treated animals were significantly decreased when compared to controls at any time point studied. However, no change in serum 3′,3,5-triiodothyronine (T3) levels were found.
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Thyroxine 5'-Deiodinase type II activity in chick pineal and Harderian gland: nyctohemeral rhythmicity and its regulation by noradrenergic input.
Journal of pineal research, 1993Co-Authors: Amalia Rubio, Armando Menendez-pelaez, Russel J. ReiterAbstract:Circadian rhythmicity of type II Thyroxine 5'-Deiodinase (5'-D) activity was studied in the pineal gland and Harderian glands of chicks. Only Harderian 5'-D activity showed a nyctohemeral rhythmicity with a maximal peak during the day time (1300), while no rhythm of enzyme activity was found in the pineal gland. Besides type II 5'-D activity, we found high basal levels of the type I isoenzyme in both glands; this activity was specifically suppressed by the addition of 6-n-propyl-thiouracil (PTU). However, day-night differences in Harderian 5'-D activity were maintained even after the addition of PTU. This activity was not affected for either continuous light exposure or darkness during the day. 5'-D activity seems to be regulated by the noradrenergic input, since the enzymatic activity was stimulated by a beta-adrenergic agonist, isoproterenol, and by the alpha-adrenergic agonist, phenylephrine, in both pineal and Harderian glands. Both drugs affected 5'-D activity in the Harderian gland by stimulating the enzyme activity over basal levels.
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Adrenalectomy or superior cervical ganglionectomy modifies the nocturnal increase in rat pineal type II Thyroxine 5'-Deiodinase.
Chronobiology international, 1993Co-Authors: Juan Ramón Jiménez, Amalia Rubio, Russel J. Reiter, C. Osuna, Juan M. GuerreroAbstract:We studied the response of type II Thyroxine 5′-Deiodinase (5′-D) activity to superior cervical ganglionectomy (SCGX) or adrenalectomy (ADX) in the rat pineal gland and other tissues. The results show that no difference was found between controls and SCGX animals during the day, but at night, SCGX modified the day-night cycle of 5′-D activity in the pineal gland. In the same way, ADX did not modify the enzyme activity during the day in pineal gland, harderian gland, hypophysis, or brain frontal cortex (BFC). However, in brown adipose tissue (BAT), where thyroid hormone metabolism is extremely dependent on α1-adren-ergic stimulation by blood circulating catecholamines, 5′-D activity is significantly decreased. At the time point of maximal pineal 5′-D activity in controls (02:00 h), ADX animals did not exhibit the nocturnal increase of the enzyme activity that occurs with control rats. Moreover, at 04:00 h ADX did not show any effect on pineal 5′-D activity. These results seem to suggest that the presence o...
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In vivo activation of pineal N-acetyltransferase but not type II Thyroxine 5'-Deiodinase by phenylephrine in young rats.
Neuroscience letters, 1991Co-Authors: Amalia Rubio, Carmen Osuna, Juan Ramón Jiménez, Patrocinio Molinero, Juan M. GuerreroAbstract:Abstract The regulation by α- and β-adrenergic agonists of pineal N -acetyltransferase (NAT) and type II Thyroxine 5′-Deiodinase (5′-D) in rats at either 2 or 6 weeks of age was studied. The pattern of stimulation was different because NAT activity could be clearly activated by an α-adrenergic agonist, phenylephrine, only in 2-week-old rats. However, isoproterenol, a β-adrenergic agonist, was able to stimulate NAT activity in rats at both 2 and 6 weeks of life. On the other hand, phenylephrine was always ineffective in stimulating 5′-D activity, while isoproterenol clearly activated it at both ages. These results strongly suggest a role for α-adrenergic receptors, in addition to β-adrenergic receptors, in regulating rat pineal NAT activity during development.
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Nyctohemeral rhythmicity of type II Thyroxine 5′-Deiodinase activity in the pineal gland but not in the Harderian gland of the Swiss mouse
Bioscience Reports, 1991Co-Authors: Amalia Rubio, Carmen Osuna, M. A. Lopez-gonzalez, R. J. Reiter, J. M. GuerreroAbstract:Type II Thyroxine 5′-Deiodinase (5′-D) activity in both pineal and Harderian glands of the Swiss mouse was studied. Pineal 5′-D activity exhibited a nyctohemeral profile with a maximal peak value at 05.00 h, which coincides with that for pineal melatonin production. However, no rhythm of 5′-D activity in the Harderian gland could be found. In pineal gland, light at night inhibited the nocturnal increase in 5′-D activity, while isoproterenol, a β-adrenergic agonist, could not stimulate the enzyme. In the Harderian gland, neither darkness, nor light at night, or isoproterenol were capable of modifying basal values of 5′-D activity.
Carmen Osuna - One of the best experts on this subject based on the ideXlab platform.
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VIP receptor-effector system in rat harderian gland and its coupling to activation of type II Thyroxine 5'-Deiodinase.
Peptides, 1995Co-Authors: Juan R. Calvo, Carmen Osuna, Maria Isabel Caraballo, David Pozo, Juan José Segura, Juan M. GuerreroAbstract:Vasoactive intestinal peptide (VIP) receptors were investigated in rat Harderian gland membranes using [125I]VIP as ligand. The receptor binding was rapid, reversible, saturable, specific, and dependent on time, temperature, and membrane concentration. At 30 degrees C, the stoichiometric data suggested the presence of two classes of VIP receptors with Kd values of 0.36 +/- 0.06 and 65.37 +/- 8.08 nM and binding capacities of 323 +/- 54 and 39,537 +/- 3100 fmol VIP/mg protein, respectively. The interaction showed a high degree of specificity, as suggested by competitive displacement experiments with several peptides structurally or not structurally related to VIP. The binding of [125I]VIP to membranes was sensitive to guanine nucleotides in a dose-dependent manner. The molecular characterization of VIP receptors was realized by chemical cross-linking; sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized membrane proteins revealed the presence of two specific [125I]VIP-protein complexes of M(r) 57 and 35 kDa as estimated in denaturing conditions. VIP stimulated adenylate cyclase activity in rat Harderian gland membranes in a dose-dependent manner. Finally, VIP stimulated in vivo the type II Thyroxine 5'-Deiodinase activity. These results demonstrate the presence of specific and functional VIP receptors in Harderian gland and suggest a role for VIP in the physiology of this gland.
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Expression of type II Thyroxine 5′‐Deiodinase from rat Harderian gland in Xenopus laevis oocytes
FEBS letters, 1994Co-Authors: Juan F. Garcia-macias, Juan M. Guerrero, Patrocinio Molinero, Carmen OsunaAbstract:The presence of isoenzymes mediating the conversion of Thyroxine to 3,5,3′-triiodothyronine has been studied according to characteristic kinetics and physiological regulation. In this paper, we report the expression of type II 5′-Deiodinase (5′D) activity in oocytes of Xenopus laevis. Oocytes injected with total RNA extracted from rat Harderian gland, and then incubated up to five days demonstrated a progressive increase in 5′D activity, reaching a maximal value at 24 h; then, 5′D activity remained almost stable for an additional period of four days. Characteristics of the enzyme activity expressed by oocytes included its inhibition by iopanoic acid, but not by propylthiouracil, and its increase during β-adrenergic agonist treatment and hypothyroidism. The expressed activity manifests characteristics typical of the type II isoenzyme. Deiodinating activity in oocytes also exhibited diurnal variations. In this study, 5′D activity expressed in oocytes exhibited low values when animals were killed during the day, and high values when animals were killed at night. Maximal values were reached 3–4 h before the nocturnal peak of 5′D activity in Harderian gland crude homogenates. Results suggest that the in vivo activation of 5′D by isoproterenol, hypothyroidism, or dark exposure may be caused by an increase in the synthesis and/or maturation of the RNA expressing the enzyme.
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effect of chronic ethanol administration on the rat pineal n acetyltransferase and Thyroxine type ii 5 Deiodinase activities
Bioscience Reports, 1993Co-Authors: Juan Ramón Jiménez, Carmen Osuna, Amalia Rubio, Juan M. GuerreroAbstract:Chronic ethanol intake resulted in a significant decrease in the rate of rat ponderal growth and an impaired nyctohemeral profile of pineal N-acetyltransferase (NAT) activity. In ethanol-treated animals, the onset of the nocturnal NAT increase is delayed by 2 hours when compared to control animals. Moreover, pineal NAT nocturnal peak was reached at 4 h (2 hours later than controls), while pineal type II Thyroxine 5′-Deiodinase (5′-D) nyctohemeral profile was not modified by ethanol administration. The effect of ethanol administration (12 weeks) on 5′-D activity in different tissues was also studied. Ethanol induced a 5′-D activity increase in hypothesis and brain frontal cortex, when compared to control animals. No change in 5′-D activity is observed in either pineal gland, Harderian gland, or brown adipose tissue. Since basal values of 5′-D activity in hypophysis or brain frontal cortex are particularly dependent on serum Thyroxine (T4) concentration, the effect of chronic ethanol administration on thyroid hormone levels was studied. Serum T4 levels in ethanol-treated animals were significantly decreased when compared to controls at any time point studied. However, no change in serum 3′,3,5-triiodothyronine (T3) levels were found.
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In vivo activation of pineal N-acetyltransferase but not type II Thyroxine 5'-Deiodinase by phenylephrine in young rats.
Neuroscience letters, 1991Co-Authors: Amalia Rubio, Carmen Osuna, Juan Ramón Jiménez, Patrocinio Molinero, Juan M. GuerreroAbstract:Abstract The regulation by α- and β-adrenergic agonists of pineal N -acetyltransferase (NAT) and type II Thyroxine 5′-Deiodinase (5′-D) in rats at either 2 or 6 weeks of age was studied. The pattern of stimulation was different because NAT activity could be clearly activated by an α-adrenergic agonist, phenylephrine, only in 2-week-old rats. However, isoproterenol, a β-adrenergic agonist, was able to stimulate NAT activity in rats at both 2 and 6 weeks of life. On the other hand, phenylephrine was always ineffective in stimulating 5′-D activity, while isoproterenol clearly activated it at both ages. These results strongly suggest a role for α-adrenergic receptors, in addition to β-adrenergic receptors, in regulating rat pineal NAT activity during development.
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Nyctohemeral rhythmicity of type II Thyroxine 5′-Deiodinase activity in the pineal gland but not in the Harderian gland of the Swiss mouse
Bioscience Reports, 1991Co-Authors: Amalia Rubio, Carmen Osuna, M. A. Lopez-gonzalez, R. J. Reiter, J. M. GuerreroAbstract:Type II Thyroxine 5′-Deiodinase (5′-D) activity in both pineal and Harderian glands of the Swiss mouse was studied. Pineal 5′-D activity exhibited a nyctohemeral profile with a maximal peak value at 05.00 h, which coincides with that for pineal melatonin production. However, no rhythm of 5′-D activity in the Harderian gland could be found. In pineal gland, light at night inhibited the nocturnal increase in 5′-D activity, while isoproterenol, a β-adrenergic agonist, could not stimulate the enzyme. In the Harderian gland, neither darkness, nor light at night, or isoproterenol were capable of modifying basal values of 5′-D activity.
Patrocinio Molinero - One of the best experts on this subject based on the ideXlab platform.
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continuous light exposure modifies the nocturnal increase in rat thymus type ii Thyroxine 5 Deiodinase
Cellular and Molecular Life Sciences, 1997Co-Authors: Mohammed Soutto, Patrocinio Molinero, Juan M. GuerreroAbstract:In the present study we show that thymus type II Thyroxine Deiodinase activity exhibits a nyctohemeral profile, with basal values during the day and high values at night. This rhythmic character is dependent on neuroadrenergic input since exposure to continuous light at night completely abolished the nocturnal rise of the enzyme activity. However, treatment with isoproterenol under light exposure at night restored it.
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β- and α-adrenergic mechanisms are involved in regulating type II Thyroxine 5′-Deiodinase in rat thymus
Life sciences, 1996Co-Authors: Mohammed Soutto, Juan M. Guerrero, Patrocinio MolineroAbstract:Abstract The role of adrenergic receptors in regulation of rat thymus type II Thyroxine 5′-Deiodinase (5′-D) activity was investigated. Our results show that norepinephrine, an α- and β-adrenergic agonist elicited an increase in thymus 5′-D activity. Isoproterenol, a β-adrenergic agonist, also increased the enzyme activity, being less effective than norepinephrine. Moreover, α-adrenergic agonists, i.e., methoxamine, an α 1 -agonist, and clonidine, an α 2 -agonist, did not increase 5′-D activity. The effect of isoproterenol was potentiated by methoxamine, but the potentiating effect was observed only at doses of isoproterenol which induce submaximal activation of the enzyme. Administration of propranolol, a β-adrenergic blocker, and prazosin, an α 1 -adrenergic blocker, inhibited significantly the activation of the enzyme induced by norepinephrine. However, yohimbine, an α 2 -adrenergic blocker, had small effect These results show, in hypothyroid rats, a clear regulation by adrenergic mechanisms of 5′-D activity in the thymus, where α- and β-adrenergic receptors might be involved.
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β and α adrenergic mechanisms are involved in regulating type ii Thyroxine 5 Deiodinase in rat thymus
Life Sciences, 1995Co-Authors: Mohammed Soutto, Juan M. Guerrero, Patrocinio MolineroAbstract:Abstract The role of adrenergic receptors in regulation of rat thymus type II Thyroxine 5′-Deiodinase (5′-D) activity was investigated. Our results show that norepinephrine, an α- and β-adrenergic agonist elicited an increase in thymus 5′-D activity. Isoproterenol, a β-adrenergic agonist, also increased the enzyme activity, being less effective than norepinephrine. Moreover, α-adrenergic agonists, i.e., methoxamine, an α 1 -agonist, and clonidine, an α 2 -agonist, did not increase 5′-D activity. The effect of isoproterenol was potentiated by methoxamine, but the potentiating effect was observed only at doses of isoproterenol which induce submaximal activation of the enzyme. Administration of propranolol, a β-adrenergic blocker, and prazosin, an α 1 -adrenergic blocker, inhibited significantly the activation of the enzyme induced by norepinephrine. However, yohimbine, an α 2 -adrenergic blocker, had small effect These results show, in hypothyroid rats, a clear regulation by adrenergic mechanisms of 5′-D activity in the thymus, where α- and β-adrenergic receptors might be involved.
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type ii Thyroxine 5 Deiodinase in the rat thymus
Journal of Endocrinology, 1995Co-Authors: Patrocinio Molinero, C. Osuna, Juan M. GuerreroAbstract:In the present study we have shown type II Thyroxine 5'-deiodination (5'D) in the rat thymus. The enzyme activity was identified in crude extract homogenates by measuring the 125 I released from [3',5'- 125 I]Thyroxine which is used as a substrate of the reaction. The release of 125 I is dependent on protein tissue concentration, time, temperature and pH, and is saturable by increasing the substrate concentration, indicating its enzymatic nature. Characteristics of the enzyme activity also include a low K m (9.1 nM), its dependence on dithiothreitol, and its inhibition by iopanoic acid, but not by propylthiouracil. Experiments to investigate the cellular location of the enzyme in the thymic gland showed that the enzyme is present in both stromal cells and thymocytes. At the subcellular level, 5'D activity was associated with cellular membranes. Thyroid status appears to regulate 5'D activity in rat thymus. Hypothyroidism caused an increase in thymus 5'D activity. The K m value remained unchanged (9.1 vs 10.5 nM) during hypothyroidism, but V max increased significantly from 17.7 fmol/mg protein per h in euthyroid rats to 53.5 fmol/mg protein per h in hypothyroid rats. 5'D activity was also modulated by catecholamines through β-adrenergic receptors because isoproterenol, but not methoxamine or clonidine, could activate the enzyme. Because these characteristics define the type II iodothyronine-deiodinating pathway in other tissues, we suggest that the rat thymus also shares this pathway.
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Type II Thyroxine 5′-Deiodinase in the rat thymus
The Journal of endocrinology, 1995Co-Authors: Patrocinio Molinero, C. Osuna, Juan M. GuerreroAbstract:In the present study we have shown type II Thyroxine 5'-deiodination (5'D) in the rat thymus. The enzyme activity was identified in crude extract homogenates by measuring the 125 I released from [3',5'- 125 I]Thyroxine which is used as a substrate of the reaction. The release of 125 I is dependent on protein tissue concentration, time, temperature and pH, and is saturable by increasing the substrate concentration, indicating its enzymatic nature. Characteristics of the enzyme activity also include a low K m (9.1 nM), its dependence on dithiothreitol, and its inhibition by iopanoic acid, but not by propylthiouracil. Experiments to investigate the cellular location of the enzyme in the thymic gland showed that the enzyme is present in both stromal cells and thymocytes. At the subcellular level, 5'D activity was associated with cellular membranes. Thyroid status appears to regulate 5'D activity in rat thymus. Hypothyroidism caused an increase in thymus 5'D activity. The K m value remained unchanged (9.1 vs 10.5 nM) during hypothyroidism, but V max increased significantly from 17.7 fmol/mg protein per h in euthyroid rats to 53.5 fmol/mg protein per h in hypothyroid rats. 5'D activity was also modulated by catecholamines through β-adrenergic receptors because isoproterenol, but not methoxamine or clonidine, could activate the enzyme. Because these characteristics define the type II iodothyronine-deiodinating pathway in other tissues, we suggest that the rat thymus also shares this pathway.
J. M. Guerrero - One of the best experts on this subject based on the ideXlab platform.
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Continuous light exposure modifies the nocturnal increase in rat thymus type II Thyroxine 5′-Deiodinase
Cellular and Molecular Life Sciences CMLS, 1997Co-Authors: Mohammed Soutto, P. Molinero, J. M. GuerreroAbstract:In the present study we show that thymus type II Thyroxine Deiodinase activity exhibits a nyctohemeral profile, with basal values during the day and high values at night. This rhythmic character is dependent on neuroadrenergic input since exposure to continuous light at night completely abolished the nocturnal rise of the enzyme activity. However, treatment with isoproterenol under light exposure at night restored it.
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Effect of chronic ethanol administration on the rat pineal N-acetyltransferase and Thyroxine type II 5′-Deiodinase activities
Bioscience Reports, 1993Co-Authors: J. Jimenez, C. Osuna, A. Rubio, J. M. GuerreroAbstract:Chronic ethanol intake resulted in a significant decrease in the rate of rat ponderal growth and an impaired nyctohemeral profile of pineal N-acetyltransferase (NAT) activity. In ethanol-treated animals, the onset of the nocturnal NAT increase is delayed by 2 hours when compared to control animals. Moreover, pineal NAT nocturnal peak was reached at 4 h (2 hours later than controls), while pineal type II Thyroxine 5′-Deiodinase (5′-D) nyctohemeral profile was not modified by ethanol administration. The effect of ethanol administration (12 weeks) on 5′-D activity in different tissues was also studied. Ethanol induced a 5′-D activity increase in hypothesis and brain frontal cortex, when compared to control animals. No change in 5′-D activity is observed in either pineal gland, Harderian gland, or brown adipose tissue. Since basal values of 5′-D activity in hypophysis or brain frontal cortex are particularly dependent on serum Thyroxine (T_4) concentration, the effect of chronic ethanol administration on thyroid hormone levels was studied. Serum T_4 levels in ethanol-treated animals were significantly decreased when compared to controls at any time point studied. However, no change in serum 3′,3,5-triiodothyronine (T_3) levels were found.
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Adrenergic regulation of type II 5'-Deiodinase circadian rhythm in rat harderian gland.
The American journal of physiology, 1992Co-Authors: C. Osuna, R. J. Reiter, J. Jimenez, A. Rubio, J. M. GuerreroAbstract:This paper reports on the regulation of the nyctohemeral profile of type II Thyroxine 5'-Deiodinase (T45'D) activity in the rat harderian gland. Harderian gland T45'D activity exhibits a nighttime increase with maximal values late in the dark period (0200-0400 h) and basal values during the daytime. The nocturnal rise of the deiodinating activity was prevented by either exposure of animals to light at night, injecting the animals with both alpha- and beta-adrenergic receptor blockers, or bilateral superior cervical ganglionectomy (SCGx). However, adrenalectomy did not affet the enzyme activity in the harderian gland. In brown adipose tissue (BAT), where thyroid hormone metabolism is extremely dependent on alpha 1-adrenergic stimulation by blood-circulating catecholamines, adrenalectomy significantly decreased T45'D activity. Deiodinating activities in brain frontal cortex (BFC) and pituitary gland were unaffected by adrenalectomy. Unlike in the harderian gland, SCGx did not modify the T45'D activity in either BAT, BFC, or the pituitary gland. The results suggest that elevated plasma catecholamines are not required for harderian gland T45'D activation and that the nyctohemeral profile of the enzyme activity in the harderian gland is dependent on the noradrenergic input from the superior cervical ganglia.
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Nyctohemeral rhythmicity of type II Thyroxine 5′-Deiodinase activity in the pineal gland but not in the Harderian gland of the Swiss mouse
Bioscience Reports, 1991Co-Authors: Amalia Rubio, Carmen Osuna, M. A. Lopez-gonzalez, R. J. Reiter, J. M. GuerreroAbstract:Type II Thyroxine 5′-Deiodinase (5′-D) activity in both pineal and Harderian glands of the Swiss mouse was studied. Pineal 5′-D activity exhibited a nyctohemeral profile with a maximal peak value at 05.00 h, which coincides with that for pineal melatonin production. However, no rhythm of 5′-D activity in the Harderian gland could be found. In pineal gland, light at night inhibited the nocturnal increase in 5′-D activity, while isoproterenol, a β-adrenergic agonist, could not stimulate the enzyme. In the Harderian gland, neither darkness, nor light at night, or isoproterenol were capable of modifying basal values of 5′-D activity.