Inhibition Of Testosterone Synthesis Research Articles

Ethanol directly inhibits Δ 5-3β-hydroxysteroid dehydrogenase-isomerase activity in rat testis interstitial cells

Acute ethanol exposure has been demonstrated to inhibit testosterone synthesis both in vivo and in vitro ; however, the precise step(s) affected is controversial. Using intact collagenase-dispersed interstitial cells or 10,000xg supernatants of interstitial cell homogenates, studies were undertaken to determine whether ethanol specifically inhibited Δ 5-3β-hydroxysteroid dehydrogenase-isomerase activity. In both cellular preparations, varing concentrations of ethanol (2.2 – 652 mM) inhibited this enzyme activity. Because alcohol dehydrogenase activity was identified specifically in Leydig cells and because the inhibition of Δ 5-3β-hydroxysteroid dehydrogenase-isomerase activity by concentrations of ethanol normally observed in circulation of alcoholic men (2.2 – 65 mM) could be reversed by saturating concentrations of NAD + (0.2 mM) or by 4-methylpyrazole (2 mM), these results suggest that the mechanism of this inhibition is by limitation of available cofactor.

Inhibition of testosterone synthesis in the canine testis in vitro

Testicular 17β-hydroxysteroid oxidoreductase (17β-HOR) is one of the several enzymes necessary for the synthesis of testosterone, but is not required for either glucocorticoid or mineralocorticoid synthesis. Since specific inhibition of the testicular enzyme has potential contraceptive and experimental uses, the inhibitory effect of twenty steroids on 17β-HOR activity was examined in microsomal preparations of canine testes. Six steroids inhibited testosterone formation, but only 4-estrene-3,17-dione (K I=2.4 μM) and 5-androstene-3,17-dione (K I=6.8 μM) had significant inhibitory activity. The data suggest the following molecular characteristics necessary for competitive inhibition of 17β-HOR activity: (a) requirement for 17-keto group, (b) relative requirement for 3-keto group, (c) decreased inhibition with unsaturation in position 5–6, and (d) marked loss of inhibitory activity with 6β-, 11β or 19- hydroxylation, and A-ring aromatization.

Drug effects on male sexual function.

The reproductive system is considered to be particularly vulnerable to the effects of drugs. Hypothalamic neurotransmitters are sensitive to drugs that alter their synthesis, release, or action; disruption of these pathways changes the levels or patterns of secretion of the pituitary gonadotropins. Drugs also exert direct action on the gonadal functions of androgen production and spermatogenesis. Drugs that decrease testosterone levels produce a multitude of effects on male reproduction. Neuropharmacologic agents that either inhibit central nervous system (CNS) activities (e.g., analgesics, anesthetics, sedatives, tranquilizers) or stimulate CNS activities (e.g., antidepressants, stimulants, hallucinogens) modify the hypothalamic-pituitary control of the gonadotropins and prolactin. The changes in luteinizing hormone, follicle-stimulating hormone, and prolactin result in changes in libido, impotence, inability to ejaculate, testicular swelling, and gynecomastia. Narcotic drugs exert their primary effect on the hypothalamic-pituitary axis and their secondary effects on the gonads and sex accessory organs. Narcotics decrease gonadotropin secretion and stimulate prolactin secretion, both of which are inhibitory to male sexual function. With marijuana, the primary drug effect is at the level of the hypothalamus, with subsequent effects on gonadotropins and testosterone. Additional studies are needed on the association of marijuana with disruption of reproduction to resolve conflicing findings. The drugs most likely to affect suxual function are those that act on the sympathetic and parasympathetic systems. Antihypertensive drugs are likely to interfere with autonomic transmission, resulting in impotence or failure of ejaculation. However, it is difficult to determine whether this increased incidence of impotence is entirely a drug side effect of a complication of blood pressure changes. Chemotherapeutic agents, especially anticancer drugs, can cause prolonged but reversible infertility. Other drugs, including marijuana derivatives, phencyclidine, and alcohol, are believed to inhibit testosterone synthesis.

Relationship between inhibition of interstitial cell testosterone synthesis by cytochalasin B and glucose

We examined the possibility that cytochalasin B reduced LH-stimulated testosterone synthesis of Leydig cells in part by inhibiting glucose uptake. In the presence of 5.6mM glucose cytochalasin B (0.1–50μM) inhibited LH-stimulated testosterone synthesis in a dose-dependent manner, while effects with cytochalasin D or cytochalasin E were not evident until inhibitor concentrations reached 1 or 10μM. Increasing levels of glucose (0–5mM) progressively increased LH-stimulated testosterone synthesis by interstitial cells, while cytochalasin B at 1 or 10μM inhibited testosterone synthesis in a dose-dependent manner at each glucose concentration examined. Higher concentrations of glucose (10– 50mM) partially reversed this inhibition. In the absence of glucose LH-stimulated testosterone synthesis was inhibited only when the cytochalasin B concentration reached 10μM. Cytochalasin B (0.1–5μM) inhibited [ 14C]-2-deoxyglucose uptake by purified Leydig cells in a dose-dependent manner, while 1 or 10μM cytochalasin D or cytochalasin E had only limited effects. These results suggest that cytochalasin B inhibits Leydig cell LH-stimulated testosterone synthesis by at least two mechanisms: by blocking glucose uptake at lower concentrations (0.1–10μM), while at higher concentrations (10–50μM) it probably blocks microfilament function.

Inhibition of testosterone synthesis by ethanol and acetaldehyde

Ethanol administration decreases plasma testosterone levels acutely in man and animals. The specific mechanism responsible for this effect is, at present, unknown. We have examined the hypothesis that ethanol or acetaldehyde directly inhibits the enzymes required for testosterone synthesis from pregnenolone. Microsomes prepared from testes of normal adult rats were isolated and assayed, in the presence and absence of ethanol or acetaldehyde, for activity of 3β-hydroxy-Δ 5-steroid dehy-drogenase (E.C.1.1.1.145)/3-oxosteroid Δ 5–Δ 4 isomerase (EC5.3.3.1) complex, testosterone 17β-dehydrogenase (ECl.1.1.64), and 17α-hydroxyprogesterone aldolase (EC4.1.2.30), three of the four enzymes required for the biosynthesis of testosterone from pregnenolone. Ethanol at levels commonly seen in the blood of chronic alcohol-ingesting men was shown to inhibit the activity of 17α-hydroxyprogesterone aldolase in a concentration-dependent manner. In addition, acetaldehyde was shown to act as an inhibitor of 17α-hydroxyprogesterone aldolase in the presence of androstenedione.

Evidence for the involvement of lutropin-independent RNA synthesis in Leydig cell steroidogenesis

The effect of incubating purified Leydig cells in Eagle's medium and the subsequent effect of the RNA synthesis inhibitors, actinomycin D and cordycepin, on lutropin-stimulated testosterone synthesis have been investigated. The inhibiting effect was found to be inversely related to the time of preincubation; with cells preincubated for 0, 1, 2 and 3 h with Eagle's medium only, followed by 2-h incubation with lutropin with and without actinomycin D, testosterone synthesis was inhibited by 37 ± 4, 31 ± 3, 18 ± 4 and 14 ± 3% respectively (means ± s.e.m., n = 5). In cells that had been preincubated for 3 h there was no significant effect of actinomycin D on testosterone synthesis during the first hour of incubation with lutropin. Thereafter the inhibition increased with time reaching a maximum of 30% after 5 h. The effects of preincubation were not due to endogenous lutropin in the Leydig cells because cells isolated from hypophysectomized rats gave similar results. The inhibition of [ 3H]uridine incorporation into the Leydig cell RNA was 80 ± 1% with 8 μg/ml actinomycin D. Increasing the concentration of this inhibitor to 80 μg/ml did not significantly increase the inhibition of [ 3H]uridine incorporation or lutropin-stimulated steroidogenesis in preincubated and non-preincubated cells. With cordycepin the inhibition of both RNA synthesis and lutropin-stimulated testosterone synthesis in non-preincubated cells were the same; with 25.1–251 μg/ml approx. 30–70% resp. With preincubated cells (3 h), 0–50% inhibition of testosterone synthesis was obtained respectively. The inhibitory effect of actinomycin D on dibutyryl cyclic AMP stimulation of preincubated and non-preincubated cells was similar to that obtained with lutropin. These observations suggest that during preincubation and independently of lutropin, synthesis of intermediates, including RNAs required for stimulation of steroidogenesis, takes place and that subsequent stimulation of steroidogenesis by lutropin occurs without further de novo RNA synthesis. These results provide evidence for a permissive role of specific RNA and protein synthesis in the action of lutropin on testosterone synthesis in the Leydig cell.

Gynecomastia induced in normal males by spironolactone.

The short‐term (1 week) and long‐term (10 month) effects of spironolactone have been determined in normal males. There were no adverse effects or changes in plasma testosterone, luteinizing hormone, or progesterone levels during one week of treatment with spironolactone (200 mg/day) in 6 normal men. A continuous 4‐hr sampling technique to provide an integrated plasma sample resulted in plasma hormone concentrations similar to the mean values for intermittent sampling. There was considerable intraindividual variability in the levels of each hormone. To evaluate the long‐term effects of spironolactone, 30 normal males were randomly divided into three groups: placebo, 100 mg spironolactone per day (low dose), and 100 mg spironolactone per day increased at two months to 200 mg spironolactone per day (high dose). The study was double blind and lasted 10 months. The presence of gynecomastia was determined clinically and confirmed by thermography. Two metabolic clearance studies with either 3H‐testosterone or 3H‐androstenedione were obtained (1) just before spironolactone treatment and (2) again with the same steroid either the last day of the 10‐month treatment period or with the development of gynecomastia. The concentrations of testosterone, estradiol, estriol, luteinizing hormone, follicle stimulating hormone, progesterone, and prolactin were also determined before treatment and at two‐month intervals during treatment. Eighteen individuals received spironolactone (10 in the low‐dose group and 8 in the high‐dose group); of these, 8 developed gynecomastia. There were none in the placebo group. The incidence of gynecomastia was 30% in the low‐dose group and 62% in the high‐dose group. In addition, one individual in the high‐dose group discontinued taking the drug early because of decreased libido, bringing the incidence of adverse effects in this high‐dose group to 75%. Spironolactone induced no significant changes in the metabolic clearance of androstenedione or testosterone. Plasma concentrations of the various hormones did not change as a result of either spironolactone or the development of gynecomastia. Inhibition of testosterone synthesis or alteration in its metabolic clearance by spironolactone does not appear to be the cause of spironolactone‐induced gynecomastia in man.

33. On inhibition of testosterone synthesis by the rat Leydig cells following incubation with gonadotropin inhibiting material from human urine

33. On inhibition of testosterone synthesis by the rat Leydig cells following incubation with gonadotropin inhibiting material from human urine

Effect of Chronic Ethanol Ingestion on the Structure and Function of Liver, Adrenals and Testes of Male Rats

Ethanol was given as a 15% (v/v) solution in the drinking water to male rats for 58–108 weeks. There was no evidence of true induction of hepatic microsomal enzyme activity nor of fatty liver. Biphenyl- and aniline-4-hydroxylase activities were increased, however, probably due to enzyme activation resulting from removal of bound endogenous substrate by ethanol rather than to new enzyme protein synthesis. Treated animals had markedly enlarged adrenal glands but adrenal histology and serum corticosterone levels were unaffected. The testes were increased in size and weight but their histological appearance was normal. Plasma testosterone levels were lower than in controls and plasma LH levels were markedly elevated. Plasma testosterone protein binding capacity was normal. It is postulated that an early effect of ethanol on the testis is to inhibit testosterone synthesis leading to a compensatory increase in plasma LH secretion and secondary testicular hypertrophy. The findings are discussed in relation to other experimental studies and their possible relevance to human alcoholism.

Studies on the Inhibition of Fetal Androgen Formation. Inhibition of Testosterone Synthesis in Rat and Rabbit Fetal Testes with Observations on Reproductive Tract Development

Groups of pregnant rats were injected with 2α-cyano-4,4,17α-trimethyl-17p-hydroxyandrost- 5-en-3-one (WIN) at varying dosage and frequency. Injections of 120-240 mg/kg body wt resulted in male fetuses with markedly reduced anogenital distances and hypospadias, but with unaffected differentiation of the reproductive ducts and of the urogenital sinus. Fetuses of rats injected with WIN or corn oil (control) at 14.5 to 16.5 days post coitum were examined on day 20.5 for testicular in vitro metabolism of 4-14C-pregnenolone and of 4-14C-dehydroepiandrosterone. Control testes converted each substrate primarily to 14C-testosterone and 14C-androstenedione. WIN-exposed testes synthesized markedly diminished amounts of 14C-testosterone and 11Candrostenedione, but accumulated Δ5-3β-hydroxysteroids: 14C-17α-hydroxypregnenolone,14Cdehydroepiandrosterone, plus residual substrate from 4-14C-pregnenolone, and 14C-androstenediol and residual substrate from 4-14C-dehydroepiandrosterone. Fetal testes of both the control and ...

Control of citrate and acetoacetate synthesis in rat liver

The mechanisms by which ethanol (EtOH) inhibits the human chorionic gonado-tropin (hCG)-stimulated testosterone synthesis was studied in isolated rat Leydig cells in vitro. EtOH inhibited steroidogenesis, but this inhibition was reversed by l-glutamate (Glu) and an uncoupler of the oxidative phosphorylation, 2,4-dinitrophenol (DNP). The mechanism of EtOH-induced inhibition was studied by measuring steroidogenic precursors and comparing them with the cytosolic and mitochondrial NADH redox states during uncoupling or in the presence of Glu. DNP had a dual effect. Low concentrations abolished the EtOH-induced inhibition of progesterone to testosterone formation suggesting that the inhibitory step was at or before progesterone formation. A large concentration led to an overall decrease in steroidogenesis indicating toxic effects on steroidogenesis. The mitochondrial NADH/NAD+ ratio, measured as the 3-hydroxybutyrate/acetoacetate ratio, decreased simultaneously when steroidogenesis was stimulated, either during uncoupling or in the presence of Glu, whereas cytosolic NADH/NAD+ ratio, measured as lactate/pyruvate ratio showed no response. These results demonstrate that the rise in the mitochondrial NADH/NAD+ ratio rather than in the cytosolic one is connected with the inhibition of testosterone synthesis by EtOH in isolated Leydig cells. The EtOH-induced high mitochondrial NADH/NAD+ ratio may deplete mitochondrial oxalacetate concentrations. This can decrease the activity of several transport shuttles and interrupt the flow of mitochondrial citrate into the smooth endoplasmic reticulum, which then reflects to decreased rate of steroidogenesis in the presence of ethanol.