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PubMed1985

Effects of age and luteinizing hormone antiserum on human chorionic gonadotropin-stimulated testosterone secretion in young male rats.

The steroidogenic capacity of young male rats of different ages was studied. Two days prior to sacrifice at 5, 10, 15, 20, 25 and 30 days of age, the rats in treatment groups were given intramuscularly either human chorionic gonadotropin (HCG) at 20 I.U. twice daily/rat or luteinizing hormone (LH) antiserum (AS) at 0.25 ml twice daily/rat. Either saline or normal sheep serum (NSS) was given to control rats. The serum and testicular testosterone concentrations in the control rats averaged 0.85 +/- 0.03 ng/ml and 1.35 +/- 0.06 ng/mg testicular protein, respectively. At day-15 the serum and testicular testosterone concentrations in the HCG-treated rats had significantly increased to 9.30 +/- 0.85 ng/ml and 11.92 ng/mg of testicular protein, respectively. At the same age, the HCG-induced higher levels of serum and testicular testosterone concentrations were significantly reduced to 2.80 +/- 0.70 ng/ml and 6.02 +/- 1.00 ng/mg protein by concomitant administration of LH/AS and HCG. Our results suggest that the testosterone production in response to HCG stimulation is age-related. It was also determined that neutralization of circulating gonadotropin in LH/AS-treated rats decreased the sensitivity of Leydig cells to gonadotropin stimulation. This in vivo model should provide an excellent opportunity for the investigation of the testicular function in developing young males.

Age Factors↗
PubMed1998

Furazolidone treatment suppresses pubertal testosterone secretion in male broiler breeder birds (Gallus domesticus).

We determined the effect of chronic administration of furazolidone (Fz) on sexual maturation of male broiler breeder birds (Ross 308; Gallus domesticus). A total of 20 15-w-old birds were randomly assigned to receive 0, 150, 250 or 350 mg Fz/kg feed daily for 5-w. Blood samples were taken at weekly intervals. The birds were challenged with 500 IU human chorionic gonadotropin (hCG) i.v. at the age of 24 w before slaughtering. Concentration of testosterone in the plasma was measured by a specific radioimmunoassay. Testicular tissue was processed for morphometric studies. Testicular weights of the groups fed 250 or 350 mg Fz/kg feed/d were decreased (P < 0.05). Plasma testosterone levels were affected by age (P < 0.001) and dose of Fz (P < 0.001). Mean plasma testosterone levels during and after drug administration were reduced (P < 0.05) by all Fz doses. Human chorionic gonadotropin administration led to poor testosterone response (P < 0.05) in all Fz-dosed groups, but not the control group (P < 0.05). As compared to the control, Fz-dosing reduced the seminiferous tubule diameter (P < 0.05) at the 350 mg/kg feed dose, seminiferous epithelial height (P < 0.05) at the 250 and 350 mg/kg feed doses, and Leydig cell nuclear diameter (P < 0.05) at the 350 mg/kg feed dose. This data suggest that sexual maturation in male broiler breeder birds is adversely affected by chronic Fz-administration. Actions of Fz on sexual maturation probably involve a direct effect at the testicular level.

Animals↗
PubMed1977

Relationship between testicular blood flow, testosterone secretion and spermatogenic activity in young and adult wild red foxes (Vulpes vulpes).

Testicular capillary blood flow (TCBF) was measured by the radioactive inert gas clearance technique throughout the reproductive life of young adult foxes and was related to the spermatogenic and androgenic activities of the testis. Mean (+/-S.E.M.) blood flow (ml min-1 g-1) was maximal in January in adults during the mating period (0-65 +/- 0-03), and in pubertal animals (0-62 +/- 0-04). At this time spermatozoa were observed in the testes of all animals, but testicular weight and circulating testosterone levels were lower in the pubescent foxes than in the adults. TCBF was minimal during immaturity (0-29 +/- 0-03) and during the resting period of the adult (0-12 +/- 0-01). These values were associated with a low testosterone level and with the multiplication of gonocytes in the young or with the seasonal very low spermatogenic activity in the adult. During the prepubertal period, TCBF slowly increased and was accompanied by testicular growth. In the adult, in September, TCBF rapidly increased without changes of testicular size and then slowly increased as the testes enlarged. High plasma testosterone concentrations occurred later. During the period of testicular regression, TCBF, testicular size, spermatogenic and androgenic activities decreased together.

Aging↗
PubMed1995

Immunocytochemical demonstration of peroxisomes in cultured Leydig cells: a decrease in testosterone secretion precedes reduction of peroxisomes.

Peroxisomes were visualized in primary cultures of mouse Leydig cells by light microscopic immunocytochemical demonstration of catalase and two enzymes of peroxisomal lipid beta-oxidation: acyl-CoA oxidase and 3-ketoacyl-CoA thiolase. Immunofluorescent peroxisomes had the form of granules, rods or short tubules located in the cytoplasm of Leydig cells. The amount of peroxisomes in the cells and the intensity of their fluorescence was similar irrespective of the antibody used. On days 2 and 4 of the culture, most Leydig cells contained very numerous, densely packed peroxisomes. On days 6 and 8, their number and fluorescence intensity gradually decreased. The parallel measurements of testosterone concentration in the culture medium revealed a sharp decline of androgen production between days 1 and 4 of the culture. The observed precedence of the decrease in testosterone production in relation to reduction of the peroxisome number suggests that a decrease in testosterone level or factors regulating androgen synthesis may influence degradation of peroxisomes.

Acetyl-CoA C-Acyltransferase↗
PubMed1987

Effects of zeranol on reproduction in beef bulls: luteinizing hormone, follicle-stimulating hormone, and testosterone secretion in response to gonadotropin-releasing hormone and human chorionic gonadotropin.

Effects of zeranol on the maturation of the adenohypophyseal-gonadal axis were studied in beef bulls. Calves were implanted with 36 mg of zeranol at 3-month intervals from birth through 6 months of age (group 2, n = 10) or were not treated (control group 1, n = 10). After 9 months, group-2 calves were given implants of 36 mg of zeranol at 3-month intervals through 18 months of age (group 2B, n = 5) or were not reimplanted (group 2A, n = 5). Areas under the curves outlined by concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone for 6 hours after the administration of 100 micrograms of gonadotropin-releasing hormone (GnRH) were calculated. Gonadotropin-releasing hormone was administered at 3-month intervals from 1.5 through 19.5 months of age. Areas under the curves for concentrations of testosterone for 4 hours after the administration of 10,000 IU of human chorionic gonadotropin (HCG) at 4.5, 7.5, and 10.5 months or 1,000 IU at 13.5 and 16.5 months of age also were calculated. The amount of FSH released was greater (P less than 0.05) for group-2 than for group-1 calves at 4.5 and 7.5 months of age. The amount of FSH released in groups 2A and 2B tended (P less than 0.10) to be greater than that for group 1. Significant differences between groups 2A and 2B were not observed. The amount of LH released at 7.5 months of age was less for groups 1 and 2 than that at earlier ages, and the decrease was greater (P less than 0.05) for group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

A testosterone-secreting adrenal cortical adenoma.

A virilizing, gonadotrophin-responsive adrenal cortical adenoma was removed from a 54-year-old woman. Following removal of the tumour, which contained and secreted androgens and estradiol, serum gonadotrophins rose to menopausal levels and the patient experienced menopausal symptoms. Pre-operative attempts to localize the source of androgens were unsuccessful.

Adenoma↗
PubMed2004

Rapid suppression of testosterone secretion after capture in male American alligators (Alligator mississippiensis).

All reptiles studied to date show an increase in circulating corticosterone following capture. This rise in corticosterone has also been shown in a number of instances to result in a decline in reproductive steroids within hours after capture. As a result of these observations it has been considered imperative to collect blood samples as soon as possible after capture to get reliable measures of reproductive hormones. It has been claimed, however, that there is no effect of capture stress on reproductive steroids in juvenile alligators held for 2 h following capture. As we generally reject blood samples that are not collected within 15 min of capture we decided to reinvestigate the effect of short-term capture (2 h) on corticosterone and testosterone in male alligators. Four groups of alligators, ranging in size from 74 to 212 cm total length were captured in a 2-week period in May, the time of year when testosterone levels are highest. Two groups were captured during the day (eight bled at capture and again at 2 h, eight bled at 2 h only) and two at night (10 bled at capture and again at 2 h, 10 bled at 2 h only). Testosterone and corticosterone in alligators bled immediately on capture and at 2 h were not significantly different in the AM and PM samples so the results were combined (Initial bleed: corticosterone, 0.95 +/- 0.09 ng/ml, n=18; testosterone, 6.06 +/- 2.09 ng/ml, n=18. Two-hour bleed: corticosterone 15.68 +/- 1.91, n=18; testosterone, 2.75 +/- 0.79, n=18). Both the increase in corticosterone and the decline in testosterone at 2 h were significant (p<0.05). Corticosterone and testosterone in the alligators sampled only once at 2 h were not significantly different from the 2-h values in alligators sampled twice (corticosterone 15.04 +/- 1.29, n=18; testosterone, 1.85 +/- 0.62, n=18). These results clearly demonstrate that short-term capture stress results in a significant decline in testosterone in male alligators.

Alligators and Crocodiles↗
PubMed1992

[Effect of prolonged hemodialysis therapy on secretion of testosterone induced by luliberin in men with chronic renal insufficiency].

The effects of prolonged hemodialysis therapy on testosterone secretion have been studied in 41 men with chronic renal insufficiency. Fifteen healthy men served as control group. LH-RH stimulation test was performed in all the studied subjects. It was found that blood serum testosterone concentration is lowered in all the patients with renal insufficiency irrespective of the time of duration of hemodialysis therapy as compared to the control group. In patients dialyzed longer than 50 month testosterone level was higher than in those subjected to shorter period of hemodialysis therapy. Reactivity of testosterone secretion in LH-RH stimulation test was greater in patients dialyzed over 50 months than either in those dialyzed during the shorter period or in the controls.

Adult↗
PubMed1984

Effect of the antifertility agent, gossypol acetic acid, on the metabolism and testosterone secretion of isolated rat interstitial cells in vitro.

Gossypol acetic acid is a polyphenolic compound present in the seed of cotton plants. Its antifertility activity by inhibition of spermatogenesis was proven in a large group of animals, including man. In the present study, the direct effect of gossypol acetic acid on collagenase isolated rat I-cells (interstitial cells) was investigated. It was shown that gossypol acetic acid depressed significantly the metabolic rate of the cells. Glucose utilization was abolished by a starting dose of 100 micrograms/ml. Oxygen consumption of I-cells was reduced even at a smaller dose of gossypol (50 micrograms/ml). At these doses, the vitality of the cells remained (proven by trypan blue exclusion test). 3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) histochemical stain was slightly decreased. Increasing doses of gossypol caused a marked decrease in the vitality of I-cells and a dramatic drop in histochemical stain for 3 beta-HSD. The pH of the medium was not changed at any dose of treatment. In cultures of I-cells not stimulated by hCG, gossypol did not affect the tonic slow release of testosterone. Thus, gossypol acetic acid has a direct inhibitory effect on isolated rat I-cells, depressing cell metabolism. The failure of some of the other groups to show such an effect, especially in vivo, can be attributed to differences in the dose of treatment and strain of animals.

Animals↗
PubMed1985

The role of endogenous gonadotropin-releasing hormone in the control of luteinizing hormone and testosterone secretion in the juvenile male monkey, Macaca fascicularis.

To determine what changes occur in the activity of gonadotropin-releasing hormone (GnRH) neurons during pubertal development in primate species we tested the hypotheses that there are morphologic differences between GnRH-containing neurons in juvenile versus adult monkeys, and the low activity of the reproductive axis is governed by hypothalamic GnRH release in monkeys prior to puberty. We removed the brains from 5 juvenile and 5 adult male monkeys (Macaca fascicularis) and blocked, sectioned, and prepared each hypothalamus for light microscopic immunocytochemistry for GnRH-containing cells. The distribution and number of GnRH-containing neurons were similar in adult and juvenile brains; however, GnRH-containing perikarya in adult brains were significantly larger in total cross-sectional area (200 +/- 12 vs. 169 +/- 8 micron 2, P less than 0.05) and in cross-sectional area of the cytoplasm (139 +/- 2 vs. 88 +/- 6 micron 2, P less than 0.05) than in juvenile brains. In another group of 10 juvenile male macaques, we administered an antiserum to GnRH (Fraser #94; 2 ml/kg, i.v.) and monitored the effects on plasma luteinizing hormone (LH) and testosterone concentrations. The percentage of plasma samples with detectable LH levels decreased significantly (from 26.67 +/- 8.3% to 5.3 +/- 3.4%, P less than 0.05) after GnRH antiserum administration; however, plasma testosterone concentrations (0.08 +/- 0.02 ng/ml) remained unchanged. We conclude that during pubertal maturation in primate species there is increased synthesis and release of GnRH from a population of GnRH neurons that are active prior to puberty.

Animals↗
PubMed1991

Effect of activin A on dehydroepiandrosterone and testosterone secretion by primary immature porcine Leydig cells.

In the present study, we evaluated the effect of the homodimer activin A on immature porcine Leydig cell functions in primary culture. Activin A (0.5-100 ng/ml) reduced hCG-stimulated dehydroepiandrosterone (DHEA) accumulation in a dose- and time-dependent manner, with a maximal inhibitory effect (58% decrease) at 20 ng/ml (8 x 10(-10) M). Activin A was found not to control steroidogenesis, either through a modulation of the gonadotropin LH/hCG binding or low-density lipoprotein cholesterol binding and internalization. However, activin A significantly decreased pregnenolone (p less than 0.002) and DHEA (p less than 0.001) formation (evaluated in the presence of 10(-5) M of WIN 24540, an inhibitor of 3 beta-hydroxysteroid dehydrogenase/isomerase [3 beta-HSDI]activity) in Leydig cells maximally stimulated with hCG (3 ng/ml, 3 h) or incubated in the presence of 22R-hydroxycholesterol (5 micrograms/ml, 2 h). These findings indicate that activin A probably exerts a partial inhibitory effect on cholesterol side-chain cleavage cytochrome P450 (P450scc) activity. On the other hand, activin A significantly (p less than 0.001) enhanced the conversion of exogenous pregnenolone and DHEA (500 ng/ml) but not of progesterone and androstenedione (500 ng/ml) into testosterone, suggesting that activin A potentially enhances 3 beta-HSDI activity in Leydig cells. Activin A action on 3 beta-HSDI activity was found to be closely related to that of transforming growth factor-beta 1 (TGF beta 1), since both activin A (20 ng/ml) and TGF beta 1 (2 ng/ml) induced a comparable and non-additive increase in 3 beta-HSDI activity.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1995

Effects of a long acting somatostatin analog on pituitary, adrenal, and testicular function during rest and acute exercise: unexpected stimulation of testosterone secretion.

The purpose of this study was to delineate the possible endocrine effects of exercise-induced GH secretion. Twelve healthy adult males were studied during short (20 min) and subsequent prolonged (2 h) physical exercise and recovery period (2 h), both after injection of a long acting somatostatin analog [Sandostatin (ST); 0.1 or 0.05 mg, sc] and after a control saline injection. Additional subjects were studied during rest with similar injections of ST (0.1 mg) and saline (n = 7) or using a lower ST dose (0.01 mg; n = 6). Several venous blood samples were taken during the trials and analyzed for selected hormones, monitoring pituitary, testicular, and adrenal functions. ST injection blocked the serum GH response to short term maximal bicycle ergometer exercise, but not to the following prolonged bicycle exercise. No relationship of the exercise-associated GH increase to the concomitant endocrine responses of the adrenals and testes was observed. Unexpectedly, the higher ST doses (0.1 and 0.05 mg) increased the mean levels of serum testosterone by 18-25% in both exercise (P = 0.0017) and rest trials (P < 0.0001), respectively. ST did not affect the levels of LH, FSH, or cortisol. ST slightly increased serum sex hormone-binding globulin (3%; P = 0.021) and albumin (4%; P = 0.017) concentrations, but not that of free testosterone. Because the testosterone response to somatostatin was fast and without a simultaneous increase in LH, it was consistent with a direct testicular response. The explanation for this novel ST effect remains obscure, but it may be due to modulation of some paracrine mechanisms inhibiting testicular steroidogenesis.

Adrenal Glands↗
PubMed2002

Melatonin participates in the control of testosterone secretion from rat testis: an overview of our experience.

The androgen milieu plays an important role in the control of immunity, and melatonin (MLT) is known to modulate the immune response as well. Our recent studies have focused on the role of MLT in controlling androgen secretion from rat testis. The presence of MLT receptors, their modulation, and the effect of MLT on steroidogenesis have been studied on Percoll-purified rat Leydig cells (LCs) cultured in vitro. MLT receptors present in adult rat LCs (B(max) = 46.7 +/- 3.5 fmol/mg protein; K(d) = 88.7 +/- 6.2 pmol/l) are coupled through a pertussis toxin-sensitive G-protein and are downregulated by prolonged exposure to MLT itself. When acutely added for three hours, MLT (0.4-400 nM) inhibits T secretion in response to LH, forskolin, and GnRH, but sensitizes cAMP-dependent T secretion when present in the preincubation media (16 h). The acute inhibition of adenylyl cyclase and the block of 17-20-desmolase (with increased 17-OH-progesterone) and of calcium release from the intracellular stores, followed by sensitization of the adenylyl cyclase activity in the long term, are described as mechanisms of MLT action. Ultimately, our studies suggest that MLT is likely to control the immune response not only through its direct effects, but also by finely modulating the androgen milieu.

17-alpha-Hydroxyprogesterone↗