Metabolism of testosterone and 5α-Dihydrotestosterone in vitro by the seminiferous tubules of the mature rat

Anibal Perez Lloret, Judith Weisz

Research output: Contribution to journalArticle

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Abstract

One hundred mg seminiferous tubules (ST) from adult rat testes were incubated for 1 hr with testosterone-3H (T) or dihydrotestosterone-3H (DHT). The quantities of the metabolites, androstenedione (A), DHT, 3α-androstandiol (3α-Adiol) and its 3β-epimer (3β-Adiol) were quantified by double isotope dilution. In incubations with 0.33 nmoles of T/ml medium the percent substrate converted to these metabolites was of the order of 11% for A, 1.5% for DHT and 4% for 3α-Adiol. As the concentration of T in the medium was raised the amount of DHT formed continued to increase while that of 3α- Adiol levelled off. When the concentration of T in the medium exceeded 5.0 nmoles/ml (5.0 × 10–6M) the quantities of DHT formed exceeded that of 3α-Adiol. The reversal in ratio in favor of DHT appeared to be due to inhibition of 3α-oxidoreductase activity rather than to saturation of the 3a-oxidoreductase, its inhibition by 3α-Adiol or lack of cofactors: When DHT was used as the substrate up to 50 times more 3α-Adiol was formed than the maximum that could be obtained from T. Substituting NADH generating system for NADPH generating system did not alter 3α-oxidoreductase activity. Addition of 3α-Adiol to the incubation did not influence 3α-reduction of DHT. The inhibitory effect of T on 3a-reduction was confirmed by incubation of ST with 1.66 nmoles/ml DHT in the presence or absence of 15.0 nmoles/ml T. The presence of T reduced by 50% the amount of 3α-Adiol accumulated. Time-sequence studies indicated that DHT formation preceded that of 3α-Adiol. In incubations of ST with DHT, 3a-Adiol was the major metabolite (approx. 70% of the substrate). Small amounts of 3β-Adiol were also identified (approx. 1.5%). The profile of metabolites formed by 2–4 mg interstitial tissue from T or DHT differed from that formed by ST under identical conditions. There was relatively more A and 3β-Adiol and less DHT and 3α-Adiol formed by IT than by ST. Thus the findings in incubations of ST were unlikely to be due to contaminating IT. Estradiol and estrone were not formed from T in detectable amounts by either the ST or the IT.

Original languageEnglish (US)
Pages (from-to)1306-1316
Number of pages11
JournalEndocrinology
Volume95
Issue number5
DOIs
StatePublished - Jan 1 1974

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Seminiferous Tubules
Dihydrotestosterone
Testosterone
Oxidoreductases
In Vitro Techniques
Androstenedione
Estrone
NADP
Isotopes
NAD
Testis
Estradiol

All Science Journal Classification (ASJC) codes

  • Endocrinology

Cite this

@article{a471a04ca1ba444db1d24b5e9b3b1075,
title = "Metabolism of testosterone and 5α-Dihydrotestosterone in vitro by the seminiferous tubules of the mature rat",
abstract = "One hundred mg seminiferous tubules (ST) from adult rat testes were incubated for 1 hr with testosterone-3H (T) or dihydrotestosterone-3H (DHT). The quantities of the metabolites, androstenedione (A), DHT, 3α-androstandiol (3α-Adiol) and its 3β-epimer (3β-Adiol) were quantified by double isotope dilution. In incubations with 0.33 nmoles of T/ml medium the percent substrate converted to these metabolites was of the order of 11{\%} for A, 1.5{\%} for DHT and 4{\%} for 3α-Adiol. As the concentration of T in the medium was raised the amount of DHT formed continued to increase while that of 3α- Adiol levelled off. When the concentration of T in the medium exceeded 5.0 nmoles/ml (5.0 × 10–6M) the quantities of DHT formed exceeded that of 3α-Adiol. The reversal in ratio in favor of DHT appeared to be due to inhibition of 3α-oxidoreductase activity rather than to saturation of the 3a-oxidoreductase, its inhibition by 3α-Adiol or lack of cofactors: When DHT was used as the substrate up to 50 times more 3α-Adiol was formed than the maximum that could be obtained from T. Substituting NADH generating system for NADPH generating system did not alter 3α-oxidoreductase activity. Addition of 3α-Adiol to the incubation did not influence 3α-reduction of DHT. The inhibitory effect of T on 3a-reduction was confirmed by incubation of ST with 1.66 nmoles/ml DHT in the presence or absence of 15.0 nmoles/ml T. The presence of T reduced by 50{\%} the amount of 3α-Adiol accumulated. Time-sequence studies indicated that DHT formation preceded that of 3α-Adiol. In incubations of ST with DHT, 3a-Adiol was the major metabolite (approx. 70{\%} of the substrate). Small amounts of 3β-Adiol were also identified (approx. 1.5{\%}). The profile of metabolites formed by 2–4 mg interstitial tissue from T or DHT differed from that formed by ST under identical conditions. There was relatively more A and 3β-Adiol and less DHT and 3α-Adiol formed by IT than by ST. Thus the findings in incubations of ST were unlikely to be due to contaminating IT. Estradiol and estrone were not formed from T in detectable amounts by either the ST or the IT.",
author = "Lloret, {Anibal Perez} and Judith Weisz",
year = "1974",
month = "1",
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doi = "10.1210/endo-95-5-1306",
language = "English (US)",
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Metabolism of testosterone and 5α-Dihydrotestosterone in vitro by the seminiferous tubules of the mature rat. / Lloret, Anibal Perez; Weisz, Judith.

In: Endocrinology, Vol. 95, No. 5, 01.01.1974, p. 1306-1316.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Metabolism of testosterone and 5α-Dihydrotestosterone in vitro by the seminiferous tubules of the mature rat

AU - Lloret, Anibal Perez

AU - Weisz, Judith

PY - 1974/1/1

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N2 - One hundred mg seminiferous tubules (ST) from adult rat testes were incubated for 1 hr with testosterone-3H (T) or dihydrotestosterone-3H (DHT). The quantities of the metabolites, androstenedione (A), DHT, 3α-androstandiol (3α-Adiol) and its 3β-epimer (3β-Adiol) were quantified by double isotope dilution. In incubations with 0.33 nmoles of T/ml medium the percent substrate converted to these metabolites was of the order of 11% for A, 1.5% for DHT and 4% for 3α-Adiol. As the concentration of T in the medium was raised the amount of DHT formed continued to increase while that of 3α- Adiol levelled off. When the concentration of T in the medium exceeded 5.0 nmoles/ml (5.0 × 10–6M) the quantities of DHT formed exceeded that of 3α-Adiol. The reversal in ratio in favor of DHT appeared to be due to inhibition of 3α-oxidoreductase activity rather than to saturation of the 3a-oxidoreductase, its inhibition by 3α-Adiol or lack of cofactors: When DHT was used as the substrate up to 50 times more 3α-Adiol was formed than the maximum that could be obtained from T. Substituting NADH generating system for NADPH generating system did not alter 3α-oxidoreductase activity. Addition of 3α-Adiol to the incubation did not influence 3α-reduction of DHT. The inhibitory effect of T on 3a-reduction was confirmed by incubation of ST with 1.66 nmoles/ml DHT in the presence or absence of 15.0 nmoles/ml T. The presence of T reduced by 50% the amount of 3α-Adiol accumulated. Time-sequence studies indicated that DHT formation preceded that of 3α-Adiol. In incubations of ST with DHT, 3a-Adiol was the major metabolite (approx. 70% of the substrate). Small amounts of 3β-Adiol were also identified (approx. 1.5%). The profile of metabolites formed by 2–4 mg interstitial tissue from T or DHT differed from that formed by ST under identical conditions. There was relatively more A and 3β-Adiol and less DHT and 3α-Adiol formed by IT than by ST. Thus the findings in incubations of ST were unlikely to be due to contaminating IT. Estradiol and estrone were not formed from T in detectable amounts by either the ST or the IT.

AB - One hundred mg seminiferous tubules (ST) from adult rat testes were incubated for 1 hr with testosterone-3H (T) or dihydrotestosterone-3H (DHT). The quantities of the metabolites, androstenedione (A), DHT, 3α-androstandiol (3α-Adiol) and its 3β-epimer (3β-Adiol) were quantified by double isotope dilution. In incubations with 0.33 nmoles of T/ml medium the percent substrate converted to these metabolites was of the order of 11% for A, 1.5% for DHT and 4% for 3α-Adiol. As the concentration of T in the medium was raised the amount of DHT formed continued to increase while that of 3α- Adiol levelled off. When the concentration of T in the medium exceeded 5.0 nmoles/ml (5.0 × 10–6M) the quantities of DHT formed exceeded that of 3α-Adiol. The reversal in ratio in favor of DHT appeared to be due to inhibition of 3α-oxidoreductase activity rather than to saturation of the 3a-oxidoreductase, its inhibition by 3α-Adiol or lack of cofactors: When DHT was used as the substrate up to 50 times more 3α-Adiol was formed than the maximum that could be obtained from T. Substituting NADH generating system for NADPH generating system did not alter 3α-oxidoreductase activity. Addition of 3α-Adiol to the incubation did not influence 3α-reduction of DHT. The inhibitory effect of T on 3a-reduction was confirmed by incubation of ST with 1.66 nmoles/ml DHT in the presence or absence of 15.0 nmoles/ml T. The presence of T reduced by 50% the amount of 3α-Adiol accumulated. Time-sequence studies indicated that DHT formation preceded that of 3α-Adiol. In incubations of ST with DHT, 3a-Adiol was the major metabolite (approx. 70% of the substrate). Small amounts of 3β-Adiol were also identified (approx. 1.5%). The profile of metabolites formed by 2–4 mg interstitial tissue from T or DHT differed from that formed by ST under identical conditions. There was relatively more A and 3β-Adiol and less DHT and 3α-Adiol formed by IT than by ST. Thus the findings in incubations of ST were unlikely to be due to contaminating IT. Estradiol and estrone were not formed from T in detectable amounts by either the ST or the IT.

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