Effects of testosterone and dihydrotestosterone on spermatogenesis, rete testis fluid, and peripheral androgen levels in hypophysectomized rats

Cimetidine (Tagamet) is a reproductive toxicant in male rats affecting peritubular cells

Cimetidine (Tagamet) is a potent histaminic H2-receptor antagonist, extensively prescribed for ulcers and now available without prescription. Cimetidine is a known testicular toxicant, but its mechanism of action remains uncertain. Rats were treated i.p. with cimetidine either at 50 mg/kg or 250 mg/kg body weight for 59 days. Accessory sex organ weights, but not testis weight, were significantly reduced in the high dose treated groups. FSH levels were significantly elevated in both treated groups, but testosterone levels were unchanged. A high degree of variability characterized testis histology, with most tubules appearing normal and some tubules (15-17%) partially lacking or devoid of germ cells. Morphometry showed that although seminiferous tubule volume was not significantly changed, the volume of peritubular tissue was reduced in the high dose group. There was extensive duplication of the basal lamina, lamina densa in both apparently normal spermatogenic tubules and severely damaged tubules. Apoptotic peritubular myoid cells were also found. TUNEL labeling confirmed extensive apoptotic cell death in peritubular cells, but revealed apoptosis of vascular smooth muscle. Given that 1) peritubular myoid cell apoptosis occurs in apparently normal tubules, that 2) basal lamina disorders are found, and that 3) peritubular cells are lost from the testis, it is suggested that the primary event in cimetidine-related damage is targeted to testicular smooth muscle cells. This is the first in vivo-administered toxicant to be described that targets myoid cells, resulting in abnormal spermatogenesis.

Role of light in the mediation of acute effects of a single afternoon melatonin injection on steroidogenic activity of testis in the rat

Young adult male rats, maintained either in an LD 12 : 12 or in continuous illumination (LL) for one week, were given a single injection of 25 microg melatonin/100 g body wt or ethanolic-saline (control) at 17.00 h. Animals from each group were sacrificed at 11.00 h on the following day. The activity of two important steroidogenic enzymes, 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) and delta(5)-3 beta-hydroxysteroid dehydrogenase (delta(5)-3 beta-HSD), and serum concentrations of testosterone, were measured following highly specific and sensitive spectrophotometric techniques and RIA, respectively. A significant decrease in the activity of both the steroidogenic enzymes was noted in the testes of melatonin-treated rats maintained under normal light-dark schedules, but this response was found to be lacking in the LL rats. However, no significant changes in the level of serum testosterone were noted in either group of melatonin-treated rats from the values in respective groups of ethanolic saline-administered LD and LL rats. Exposure of ethanolic saline-injected rats to continuous light also did not cause any change in the steroidogenic activity of the testis from those in LD rats. The study indicates that continuous light as such does not affect the endocrine function of testis but abolishes suppressive effects of melatonin on the steroidogenic activity of the testis in rat.

7alpha-methyl-19-nortestosterone, a synthetic androgen with high potency: structure-activity comparisons with other androgens

CNNT. There was a good correlation between bioactivity and binding affinity to AR for the 7alpha-substituted androgens compared to T. In contrast, relative to their binding affinity to AR, the androgenic potency of DHT and 19-NT was lower compared to T. The reason for the lower in vivo androgenic activity of 19-NT is attributable to its enzymatic conversion to 5alpha-reduced-19-NT in the prostate. In the case of DHT, the lower bioactivity could be attributed to its faster metabolic clearance rate relative to T. The correlation was further investigated in vitro by co-transfection of rat ARcDNA expression plasmid and a reporter plasmid encoding the chloramphenicol acetyl transferase (CAT) gene driven by an androgen inducible promoter into CV-1 cells. All the androgens led to a dose-dependent increase in the CAT activity. MENT was found to be the most potent followed by DHT, 19-NT, T, and CNNT. The specificity of the androgenic response was confirmed by its inhibition with hydroxyflutamide, an antiandrogen. Thus, there was a good correlation between binding affinity and in vitro bioactivity in the transient transfection assay for the androgens. This suggests that the in vivo bioactivity of androgens could be influenced not only by binding affinity to receptors but also by factors such as absorption, binding to serum proteins and metabolism. However, the high potency of MENT is primarily related to its higher affinity to AR.

The use of testosterone as a male contraceptive

Testosterone functions as a contraceptive by suppressing secretion of the pituitary gonadotropins luteinizing hormone and follicle stimulating hormone. Low levels of these hormones decrease endogenous testosterone secretion from the testis and deprive developing sperm of the signals required for normal maturation. Interference with sperm maturation causes a decline in sperm production and can lead to reversible infertility in men, raising the possibility that testosterone could be utilized in a commercially available contraceptive. To this end, testosterone has been studied alone and in combination with either gonadotropin releasing hormone analogues or progestins in efforts to improve its contraceptive efficacy. In this chapter, we will review efforts to use testosterone to create a safe, convenient, efficacious contraceptive method for men.

Regulation by retinoids of luteinizing hormone/chorionic gonadotropin receptor, cholesterol side-chain cleavage cytochrome P-450, 3 beta-hydroxysteroid dehydrogenase/delta (5-4)-isomerase and 17 alpha-hydroxylase/C17-20 lyase cytochrome P-450 messenger ribonucleic acid levels in the K9 mouse Leydig cell line

Vitamin A is a potent regulator of testicular function. We have reported that retinol (R) and retinoic acid (RA) induced a down regulation of luteinizing hormone/human chorionic gonadotropin (LH/CG) binding sites in K9 Leydig cells. In the present study we evaluated the effect of R and RA on LH/CG receptors, cholesterol side-chain cleavage cytochrome P-450 (P-450 scc), 17 alpha-hydroxylase/C17-20 lyase (P-450 17 alpha) and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) mRNA levels in K9 mouse Leydig cells. To validate K9 cells as a model for studying Leydig cell steroidogenesis at the molecular level, we first investigated the effect of hCG on mRNA levels of the steroidogenic enzymes. P-450 scc, 3 beta HSD and P-450 17 alpha were expressed constitutively. The addition of 10 ng/ml hCG enhanced mRNA levels for the three genes within 2 h. Maximal accumulation of P-450 scc, P-450 17 alpha and 3 beta HSD mRNA in treated cells represents a 2.5-, 8.5- and 4-fold increase over control values, respectively. P-450 17 alpha expression reached a maximum by 4 h and then declined rapidly to return to control value by 24 h. The pattern of LH/CG receptor mRNAs in K9 cells was very similar to that of MA10 Leydig cells and showed six transcripts of 1.1, 1.6, 1.9, 2.6, 4.2 and 7.0 kb. Treatment of cells with R or RA resulted in a time- and dose-dependent decrease in all six species.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of elevated estradiol with remote testicular trauma in young infertile men

OBJECTIVE

To determine the incidence of remote testicular trauma and of possible related permanent hormonal and seminal changes in infertile men.

DESIGN

Retrospective clinical study of hormonal and seminal parameters in a subpopulation of infertile men.

SETTING

Andrology Clinic in an academic research environment.

PARTICIPANTS

Infertile men, with and without history of remote testicular trauma, and fertile volunteers.

MAIN OUTCOME MEASURES

Percentage of infertile men with history of blunt testicular trauma, concentrations of reproductive hormones, and semen parameters.

RESULTS

Significant remote blunt testicular trauma was reported by 16.8% of infertile men. This had occurred 2 to 17 years (mean, 16.4 years) before evaluation, mostly with contact sports at adolescent age. Estradiol concentrations after testicular trauma were 19% and 25% higher than in infertile men without history of testicular injury and in fertile controls. Elevated E2 levels did not correlate with T. Infertile men with and without history of testicular trauma showed changes in seminal parameters.

CONCLUSION

The incidence of remote blunt testicular trauma in infertile men is unexpectedly high. After injury, FSH-stimulated aromatization of T may increase testicular E2 production, interfere with spermatogenesis, and cause infertility. Consistent use of protective devices in contact sports is recommended.

Non-androgenic role of testis in enhancing ventral prostate growth in rats

This study was conducted to investigate whether the testis, aside from its ability to secrete androgen, is able to promote prostatic growth in rats. Increasing quantities of silastic capsules filled with crystalline dihydrotestosterone (DHT) were implanted subcutaneously into adult Sprague-Dawley rats at the time of bilateral epididymo-orchiectomy or sham operation on the testes. Control animals received empty capsules. Twenty-eight days later, the growth of the ventral prostate as measured by wet weight, DNA, and protein content per prostate was significantly greater in rats with intact testes than in orchiectomized rats. An overall increased growth was noted at all doses of exogenous DHT administered. Serum levels of luteinizing hormone in animals treated with DHT were undetectable. Serum levels of testosterone in intact rats treated with DHT were not significantly different from those in castrated rats. These observations suggest a non-androgenic role for the testis and, perhaps, epididymis in promoting prostatic growth in rats, and are consistent with the concept that a non-androgenic substance, produced from the testis and/or epididymis, is able to enhance prostate growth induced by androgen stimulation. The possibility that this phenomenon may play a role in the benign growth of the prostate observed in aging human males with decreased blood levels of androgen warrants consideration.

Dynamics of estradiol and testosterone and seminal fluid indexes in smokers and nonsmokers

The serum levels of estradiol (E2) and testosterone (T), the metabolic clearance rates of estradiol (MCRE2) and testosterone (MCRT), and the production rates of estradiol and testosterone (PRE2) and (PRT) were examined in 22 male smokers and 21 male nonsmokers. Seminal fluid indexes (sperm count, % motility, grade of motility, and % of sperm with abnormal morphology) were also assessed. The mean E2 level and the mean PRE2 were significantly greater in smokers than in nonsmokers (P less than 0.001 and P less than 0.01, respectively); however, the means of MCRE2, MCRT, PRT, and T did not differ significantly in smokers compared to nonsmokers. No significant product-moment correlations were found between the various hormonal measures and the seminal fluid indexes in the overall sample. However, the smokers with sperm counts below the median sperm count of the sample had significantly higher mean levels of E2 and PRE2 than did the smokers with sperm counts above that median. Mechanisms that might mediate the greater PRE2 of smokers and a negative relationship between estradiol and sperm count are discussed.

Hyperprolactinemia and male sexual behavior: effects of steroid replacement with estrogen plus dihydrotestosterone

To determine if alterations in the availability of the active metabolites of testosterone (T) are involved in the inhibition of sexual activity in hyperprolactinemic animals, the effects of four ectopic pituitary grafts on copulatory behavior were examined in castrated male rats given subcutaneous implants of T or estradiol-17 beta (E2) plus 5 alpha-dihydrotestosterone (DHT). Two weeks after implantation of the steroid-filled capsules, half the animals of each group were given pituitary grafts and the remainder were sham-operated. Tests of copulatory behavior were performed prior to, and one, two, and three months following pituitary transplantation. Pituitary grafting caused significant inhibition of copulatory behavior in both T and E2 + DHT treated animals. PRL levels were significantly higher in E2 + DHT treated grafted males than in T treated grafted animals (2000 +/- 140 vs. 395 +/- 26 ng/ml), but did not differ between the corresponding control groups (61 +/- 8 vs. 73 +/- 6 ng/ml). The results of these experiments preclude the possible involvement of alterations in steroid secretion by the testes or modifications of the conversion of T to its active metabolites in the effects of hyperprolactinemia on copulatory behavior.

In vivo patterns of circulating testosterone following castration and intramuscular testosterone propionate injections of adult male rats

In vivo patterns of circulating testosterone (T) were investigated in castrated and in intact male rats following a single intramuscular injection of 1mg testosterone propionate (TP). In addition, the in vivo clearance pattern of T was investigated following castration. The injection of TP into intact rats resulted in a rapid, statistically significant increase in circulating T which lasted for 12h and returned to normal by 24h post-injection. Circulating T decreased to nondetectable levels by 6h following orchiectomy. Injection of TP into castrated rats caused a rapid increase in circulating T which reached highest levels 60 min after administration. The concentrations of T in TP-treated orchiectomized rats remained elevated for 12h with a gradual decline which persisted for the experimental period of 6 days post-injection and provided moderate maintenance of sex accessory organ weights. TP injections increased circulating T levels in both groups of rats, but the magnitude of elevation was greater in intact animals where the normal T diurnal variations were disturbed. The elevation in circulating T persisted longer in the castrate-TP-treated animals than in intact animals, suggesting a difference in clearance, distribution and metabolism of T in orchiectomized rats.

Dihydrotestosterone causes reversible infertility in male rats

Dihydrotestosterone released continuously from a subcutaneously implanted Silastic elastomer was more potent than testosterone in reducing circulating gonadotropin and androgen concentrations and in inducing testicular atrophy and infertility despite normal ejaculatory function as judged by the presence of vaginal plugs in cage mates. All effects were reversible. Thus quantities of dihydrotestosterone which reduce circulating gonadotropin concentrations suffice to maintain the weights of accessory sex organs but not spermatogenesis. That the latter is possible with higher doses even in the complete absence of luteinizing hormone and follicle-stimulating hormone (state after hypophysectomy) has been shown by others.

Dose-dependent inhibition of spermatogenesis in mature rams with exogenous testosterone

Testicular and accessory sex gland function was examined in 20 mature breeding rams that received graded dosages of testosterone (T) by subdermal Silastic implants or intramuscular injections. Treatments were imposed for 72 days during the normal breeding season. As compared with control rams rams implanted with 20 T-filled Silastic capsules had greatly reduced testes (24%) and epididymides (53%) weights as well as total daily sperm production (3.3%) and epididymal sperm reserves (3.9%). These effects were produced when serum T concentrations were increased four-fold over those of control rams, serum LH was nondetectable and serum FSH was substantially decreased. Testicular weight and total daily sperm production were less dramatically reduced in rams given T (2 x 250 mg/day) by injection. In spite of the high serum T concentrations observed in injected rams, weights of the accessory sex glands were not significantly affected. Treatment with 5 or 20 T-filled Silastic capsules or by injection of T not only suppressed gonadotropin secretion and spermatogenesis but also reduced T concentrations in rete testis fluid. A high correlation (r = 0.94, P < 0.01) between daily sperm production and T concentrations in rete testis fluid was calculated in this study. Results presented herein indicate that 1) treatment of rams with exogenous T affects spermatogenesis in a dose-dependent manner and 2) spermatogenic yield is related to T concentrations in fluid of the rete testis.