Androgen-dependent Organs Research Articles

Inhibition of estrogen biosynthesis and its consequences on gonadotrophin secretion in the male

Of the gonadal steroids in the male, testosterone is the most important regulator of gonadotrophin secretion. However, whether testosterone affects gonadotrophin secretion directly or whether it must first be aromatized to estrogens is controversial. We have reported extensively on the endocrine and anti-tumor effects of the non-steroidal aromatase inhibitors CGS 16949A and CGS 20267 in adult female rats. In these animals, both inhibitors potently and selectively inhibit estrogen biosynthesis. Thus these agents can be effectively used in studying estrogen-dependent processes. CGS 16949A was administered for 14 days to adult male rats, over a dose range which in females suppresses estradiol and elevates LH. In male rats a suppression of estradiol was seen, however, there was no significant effect on either serum LH or on the weights of androgen-dependent organs. CGS 16949A, when administered to healthy men at a dose of 1 mg b.i.d. for 10 days, causes a significant fall in plasma estradiol and significant elevations of plasma FSH and testosterone. Dose-dependent suppression of serum estradiol and an increase in serum testosterone and LH are seen after administration of single oral doses of CGS 20267. These results indicate that in the male rat, inhibition of aromatization of testosterone to estrogens does not influence gonadotrophin secretion whereas in men the negative feedback exerted by testosterone on gonadotrophin secretion is dependent on the aromatization of testosterone to estrogens.

Immunohistochemical Demonstration of Androgen-Binding Protein in the Rat Prostatic Gland1

Androgen-binding protein (ABP) is one of the best-characterized products of synthesis by the Sertoli cells in the rat. Although the exact physiological role of ABP remains to be determined, it has been widely used to study Sertoli cells and testicular function in this species. Since this protein is the principal carrier for testosterone in rat testis and epididymis, we decided to investigate ABP immunoreactivity (ABP-I) in androgen-dependent organs, including testicle, epididymides, prostate, and seminal vesicles. The location of ABP was investigated by immunohistochemistry using specific antisera against rat ABP. As previously described in the testis, rat ABP-I was identified in the seminiferous tubules within the cytoplasm of the Sertoli cells and the tubular luminae. The epididymis showed ABP-I only in epithelial cells of the proximal caput. We demonstrated ABP-I in the apical portions of epithelial cells of the rat prostate. Short-term castration and/or ligation of the efferent ducts did not suppress prostatic ABP-I. ABP-I was not present in seminal vesicles of control rats nor under any of the experimental conditions used throughout this study. The results also indicate the presence of ABP-I in prostatic epithelium, probably because of a mechanism similar to that described in epididymis. Our data support and enhance the concept that ABP may serve as a transmembrane carrier protein for androgens in androgen target organs in the male reproductive tract.

Histoautoradiographic study of rRNA and mRNA transcription activity related to secretory function in lizard epididymis.

The lizard epididymis is an androgen-dependent organ whose epithelial cells undergo marked changes in structure and secretory activity during the annual cycle. These changes are connected to fluctuations of testosterone levels. During the breeding season, the epididymis produces a major protein secretion, the L-proteins. In the present work we studied the fluctuations of RNA synthesis and accumulation during the annual cycle by means of histoautoradiographic methods. Total RNA synthesis was determined by uridine incorporation; accumulation of rRNAs and L-protein mRNAs were determined by in situ hybridization. Total RNA synthesis began during reorganization (Phase I), then increased gradually during differentiation and growth (Phase II). The synthesis peaked during maturation (Phase III), but stopped abruptly during hypersecretory activity (Phase IV). The rRNAs were very abundant from Phase II to Phase IV, which is related to the presence of many ribosomes as revealed by electron microscopy. The mRNAs of L-proteins were detected only during Phases III and IV in all epithelial cells. For every phase of the sexual cycle there exists a strong correspondence between the changes in transcriptional activity (rRNA and specific mRNA) of the epithelial cells and changes in the testosterone levels.

Pharmacological Studies on Androgen Suppression in Therapy of Prostate Carcinoma

In hormone-dependent prostate carcinoma, androgens can be suppressed into the castrate range by LHRH agonists. Testosterone secretion is blocked at two levels: testicular androgens and adrenal androgens. In humans, the contribution of testicular androgens is about 95%, whereas in the rat, the adrenal androgen secretion is negligible. Pharmacological studies were performed on the suppressive effect of the LHRH agonist, buserelin on androgen-dependent organs in adult rats. The reduction in pituitary and testicular binding capacity was monitored during treatment by injection, or by long-term infusion. Marked differences in suppressive mechanisms activated by the different regimens were observed. Changes in testicular steroid biosynthesis were analysed by incubation of testes after treatment with HCG, measuring the spectrum of C21/C19-steroids in incubation media. In particular, the levels of intraprostatic androgens were determined during treatment with daily buserelin injections, or with sustained release formulations of buserelin. The tissue content of testosterone and 5-alpha-dihydrotestosterone (DHT) were both markedly lowered. In castrate rats, stimulation of adrenal function by ACTH infusion had no effect on the prostate weight or intratesticular T/DHT content. Combination therapy during the initial phase of treatment by an androgen receptor blocker (cyproterone acetate) and buserelin (infusion or implants) was more effective to suppress prostate weight and intra-prostatic T/DHT content than therapy with the single compounds alone. Spermatogenesis and fertility were suppressed after prolonged treatment periods of 6-12 months; the testicular atrophy was not reversible in these long-term injection studies. Similar studies in dogs and monkeys have shown a different result: inhibition of spermatogenesis was fully reversible. It is concluded that studies on the mechanism of androgen suppression by LHRH agonists and the effects on androgen dependent organs provide useful information for the improvement in therapy of hormone-dependent prostate carcinoma.

Reproductive tract defects induced in adult male rats by postnatal 1,2-dibromo-3-chloropropane exposure

The reproductive tract of the male rat may be particularly susceptible to chemical injury during the early postnatal period since significant developmental changes occur in the tract at that time. The subcutaneous administration of relatively low doses of 1,2-dibromo-3-chloropropane (DBCP, 5–20 mg/kg) on alternate days, from 2 to 20 days of life, resulted in a marked dose-related reduction in the testis, epididymis, and seminal vesicle weights. Histological evaluation revealed degenerative cellular changes in the testes of the 5 mg/kg treated group and obliteration of the seminiferous tubules in the 10 mg/kg treated animals. Biochemical studies showed that the in vitro androgen production capacity per unit weight of testicular tissue was elevated, as a function of the DBCP dose, correlating with the apparent increases in the Leydig cell concentrations observed histologically in the treated animals. Due to the marked reduction in the testes weight of DBCP-treated animals, the in vitro testicular androgen production rate, when expressed on the basis of testes pair weight, was reduced; it was consistent with the observed DBCP-induced decrease in serum androgen levels. Early DBCP exposure also obliterated the androgen responsiveness of the seminal vesicle and epididymis in the adult rat, which may also contribute to the diminution in the weights of these androgen-dependent organs. The present study also indicated that immature rats were more susceptible than sexually matured male rats to DBCP toxicity. Moreover, the results of the critical period study indicated that the first 10 days of life are of particular importance in the reproductive tract toxicity of DBCP.

Photoperiodic and endocrine control of social proximity behavior in male Japanese quail (Coturnix coturnix japonica).

Previous research had shown that reproductively mature male Japanese quail maintained on a 16:08 light/dark (16L:8D) photoperiod spend about 75% of their time throughout daylight hours near a window that provides visual access to a female conspecific. In contrast, females do not display a corresponding tendency to remain near male conspecifics. In Experiment 1, I demonstrated that the social proximity behavior of male Japanese quail declines significantly when photostimulation is restricted to 2 hr daily (02:22 light dark; 2L:22D), but can be restored by reinstituting the 16L:8D schedule. Changes in the photoperiod produced corresponding changes in the size of the cloacal gland, and androgen-dependent organ. The low levels of social proximity behavior and cloacal gland size of males maintained on short daily exposures to light (2L:22D) also could be reversed by sc implants of testosterone (Experiment 2), and this recovery was to some extent sensitive to testosterone dose (Experiment 3). The present studies indicate that social proximity behavior in male Japanese quail is androgen dependent and provide a behavioral assay for neurohormonal studies of sexual behavior that does not depend on brief phasic responses.

Pharmacology of antiandrogens

Principally, antiandrogens affect all androgen-dependent organs and functions as for instance accessory sexual glands, spermatogenesis, skin and skin appendages, libido and potency, male sexual differentiation, longitudinal bone growth and bone maturation. Pharmacologically, it is important to distinguish between the steroidal antiandrogens of the cyproterone acetate type and the nonsteroidal pure antiandrogens (flutamide, anandrone). For the clinical use of cyproterone acetate and similar antiandrogens in both men and women the three main properties are important: Cyproterone acetate is antiandrogenic, it is a quite potent progestogen and it is antigonadotrophic. Based on pharmacological and biochemical backgrounds cyproterone acetate is used in the following indications: Androgen mediated disorders of the skin such as acne, seborrhoea, hirsutism, alopecia, advanced prostatic carcinoma, precocious puberty and male hypersexuality. In order to avoid undesired systemic side effects local application of antiandrogens, e.g. of cyproterone acetate, has been tried several times. All these attempts have failed probably because insufficient concentration of the antiandrogen at the pilo sebaceous unit. 17α-propylmesterolone is active when given topically (hamster ear model) and has no systemic antiandrogenic effects. This antiandrogen is highly lipophilic and does penetrate preferentially through the hair follicle as has been shown by autoradiography.

Effects of castration on the epididymis of a non-mammalian vertebrate: evolution of morphology, protein synthesis, and of specific mRNA levels.

The lizard epididymis is an androgen-dependent organ undergoing large variations in its structure and in protein synthesis ability during its annual cycle. It produces a major androgen-dependent protein, the L protein. This work reports the effects of castration performed at 3 prominent points of the sexual cycle: stage 1 (epithelium reorganization) stage 3 (onset of secretory activity) stage 6 (full secretory activity). Evolution of various parameters (organ weight, histology, amount of soluble proteins, rate of soluble protein synthesis and of specific protein synthesis: L protein, and mRNA levels) was considered over a period ranging from 7 days to 15, 30 and 60 days. Deprivation of the testis was followed by an organ involution which was more or less accentuated or more or less rapid according to the stage of the operation but some peculiarities need to be emphasized. At first, the evolution of the organ was not stopped but it proceeded: at stage 1, there was cell division and a correlated increase in total protein synthesis (without L protein synthesis), at stage 3 total protein synthesis and L protein mRNA levels increased (synthesis of L protein proceeded up to 30 to 60 days), at stage 6 the involution was accelerated. These effects concerning stage 1 and particularly stage 3 appeared as a kind of a paradoxical induction. Secondly, the epithelium underwent phases of destruction and regeneration which were obviously not controlled by the testis.

Age-related reproductive decline in the male Japanese quail

A series of experiments was conducted to study the decline in reproduction associated with age in the male Japanese quail. In Experiment 1, eggs were collected from pairs that were 28, 56, 107, and 149 weeks of age. Pairs that were 56 weeks of age or older showed a sharp drop in fertility and hatchability. Subsequent experiments were designed to study the endocrine and behavioral basis for this decline in the male. In Experiment 2, males that were between 23 and 70 weeks of age were tested for mating behavior, plasma testosterone was measured, and testes wet weight was determined. There were no significant differences between the age groups. However, samples taken from an additional group of males 168 weeks of age showed significantly ( P < 0.05) lower serum testosterone and testes weight. Therefore, the third experiment was designed to include age groups of males between 4 and 126 weeks of age in order to further examine this decline in males older than 70 weeks of age. There was a significant ( P < 0.05) drop in this number of males showing sexual behavior and of those males showing sexual behavior; the quantity of mating activity also declined. Plasma testosterone was reduced in the older groups; however, the change was not significant. In addition, the size of the cloacal gland, an androgen-dependent organ, declined with age ( P < 0.05). These results argue that the age-related reproductive decline may have behavioral as well as endocrine basis. Possibly, the behavioral changes may result from altered receptor sensitivity at the level of areas of the brain, which control reproductive behavior, and at the level of the testes, which affect hormone production and spermatogenesis.

Vasculature of the mouse, rat, and rabbit testis‐epididymis

The arrangement of blood vessels serving the testis-epididymis vas investigated microscopically in the mouse, rat, and rabbit. Blood vessels were visualized by infusing liquid silicone rubber into the vessels and subsequently clearing the surrounding tissue. Comprehensive illustrations of the vasculature were prepared from three-dimensional examinations. Arterial and venous vessels serving the testis-epididymis follow similar routes in all three species. However, the arrangements and characteristics of the blood vessels demonstrate dramatic species differences. For example, arteries within the testes have tight coils in the mouse and artery-artery anastomoses in the rat. Veins form vascular pathways that connect the testis and efferent ductules in all three species but also form a connection between the testis and cauda epididymidis in the rabbit only. Testosterone concentrations were determined in blood obtained by micropuncture of selected testis-epididymal veins. The measurements establish that the highest levels of testosterone are found in testicular surface veins. Also, vas deferential veins of the rabbit had significant amounts of testosterone. Studies of the blood-vessel volumes suggested that the volumes of arteries and veins in the testis are similar, whereas venous volumes exceed arterial volumes in all of the other organs examined. The studies provide comprehensive information about the architecture and physiology of blood vessels serving the testis-epididymis in the mouse, rat, and rabbit. Each species exhibits diversity in the vasculature and testosterone content of the veins. Veins connecting the testis to the efferent ductules and cauda epididymidis may provide for the preferential delivery of testicular secretions to androgen-dependent organs before the secretions are metabolized or diluted in the systemic blood.

Biological activity of hormonally active and non-active androgen derivatives

Androgen derivatives appeared to have different biological activities in vivo and in vitro. Testosterone-17-isobutyrate given in three doses of 50 or 200 μ g increased significantly the weight of seminal vesicles and reduced thymus weight in castrated males, whereas testosterone-17-hemisuccinate, testosterone- D-β-glucoside and testosterone-3-( O-carboxymethyl)-oxime had no such effects. Similarly, ten 1-mg doses of testosterone-17-isobutyrate, unlike testosterone-17-hemisuccinate, resulted in a marked reduction of thymus weight in non-castrated males and in a significant inhibitory effect on the activity of spermatogenesis. On the other hand, all three androgen derivatives, which had appeared inactive in vivo, had similar effects in vitro (as had active testosterone) as demonstrated by inhibition of Concanavalin A-induced lymphocyte activation expressed by 14C thymidine incorporation and inhibition of cell agglutination. These results seem to suggest that as for the regulation of androgen-dependent organs and functions (such as the size of seminal vesicles, activity of spermatogenesis, thymus size), hormonally active androgens are also involved in certain immunosuppressive effects in vivo. On the other hand, in vitro immunological effects are produced by both hormonally active and non-active androgen derivatives as well as by other steroid hormones, the common denominator being the steroid structure.

Inhibitory Control of the Pituitary LH Secretion by LH-RH in Male Rats

Luteinizing hormone-releasing hormone (LH-RH) was administered to prepubertal male rats (intact, castrate or castrate-adrenalectomized, 60 g body weight) for 28 days (1 microgram LH-RH/day, s.c.), at a 10-fold physiological dose, as compared to the minimal FSH-releasing dose of 100 ng/rat s.c. In intact rats, serum LH and weight of androgen-dependent organs (vented prostate, seminal vesicles) were reduced after 14 days of treatment. In castrate rats, the postcastration rise in serum LH was abolished by treatment. Pituitary LH content, FSH secretion and prolactin secretion were not suppressed. Hypothalamic LH-RH was increased at 14 and 21 days. In castrate adrenalectomized male rats, LH secretion was also suppressed by 1 microgram LH-RH s.c. x 28 days. The hypothalamic LH-RH content did not increase. The pituitary LH-RH receptor level was not down-regulated after 14 days treatment either in intact or castrate male rats. Pituitary inhibition (LH release) in rats by a supraphysiological dose of LH-RH given for 28 days indicates that the optimal regime for chronic treatment has to be determined by monitoring LH release at regular intervals. Direct pituitary inhibition by LH-RH may explain some of the unexpected antifertility effects observed with high doses of LH-RH.

Gonadotrophin Changes in Male Rats Following a Sterilizing Dose of α‐Chlorohydrin

A single oral sterilizing dose of α‐chlorohydrin (80 mg/kg) produced obstructive retention cysts in the caput epididymis and ductuli efferentes of the male rat with resultant destruction of the spermatogenic epithelium. The weights of androgen dependent organs other than the epididymidis were not changed by the treatment, suggesting that androgen secretion was not impaired. Serum prolactin was elevated for several weeks after α‐chlorohydrin possibly correlated with a diuretic action. LH secretion was unchanged for 4 days, significantly elevated at 7 days, then slowly declined to normal, a result which could not be correlated with the other endocrine changes. Serum FSH was significantly elevated by day 4 and remained high for the period of the experiment. The results support the idea of separate controlling mechanisms for LH and FSH secretion. The rapid and persistent rise in FSH supports the view that a hormonal factor (inhibin) is normally produced by the seminiferous epithelium. The possibility that inhibin is normally absorbed via the epididymis and in these experiments fails to reach the systemic circulation because of the epididymal lesion is discussed.

GONADOTROPHIN RESPONSE AFTER CASTRATION AND SELECTIVE DESTRUCTION OF THE TESTICULAR INTERSTITIUM IN THE NORMAL AND ASPERMATOGENIC RAT

ABSTRACT Serum LH and FSH were measured by radioimmunoassay in adult male rats previously rendered aspermatogenic by a high dose of α-chlorohydrin. In the aspermatogenic rat serum FSH was elevated but LH levels and androgen dependent organ weights were within normal limits. Transient destruction of the interstitium with a resultant decrease in testicular androgen secretion by ethylenedimethane sulphonate (EDS) in the normal rat preferentially increases serum LH. However, in the aspermatogenic rat EDS increased both serum LH and FSH to levels indistinguishable from those of the normal castrate. The pattern of gonadotrophin secretion in the EDS treated aspermatogenic rat suggested that the dynamic changes after the disturbance of the androgenic feedback were faster than those found in the normal male rat. Castration of the aspermatogenic rat produced serum gonadotrophin levels comparable to the 27 day normal castrate within I and 2 days for LH and FSH, respectively. The data supports the concept of the dual control of pituitary gonadotrophin secretions arising from the seminiferous tubule (inhibin) and the interstitium (androgen). In addition the results also suggest that inhibin acts to modify pituitary sensitivity to endogenous LH-RH as the removal of the androgenic feedback signal in the aspermatogenic rat either by EDS or castration results in a faster achievement of castrate gonadotrophin levels.

Seasonal changes in testosterone levels and androgen-dependent organs in male moles (Talpa europaea).

Seasonal changes in testicular and plasma testosterone levels and in androgen-dependent organs were determined in moles breeding at 53 degrees N. Although the testes contain up to 30 times more testosterone during spermatogenesis than during sexual quiescence, appreciable quantities of this hormone are present during late summer and early autumn. Annual spermatogenesis lasts for only 2 months, but in some moles spermatozoa remain in the epididymis for up to 3 months after the testes have begun to involute, and may therefore be available to inseminate females coming into a second oestrus.

Androgen control of the sexual maturation pheromone in house mouse urine.

Changes in the capacity of male or female mouse urine to accelerate sexual maturation in female mice were measured following castration and replacement with testosterone propionate (TP). In the male pheromonal activity declined significantly within 2 days after castration and disappeared between 10-15 days. After a single 1.0 mg dose of TP activity reappeared within 24 hours and reached maximum levels within 60 hours. Pheromonal activity showed a significant correlation with urine protein levels. Pheromonal activity androgen-dependent organs and plasma testosterone increased with increasing doses of TP but total urine proteins were not significantly correlated with this activity. The activity of urine from TP-treated females equaled that from males with intact gonads. Pheromonally active urine increased body weight in young females only in some cases. The findings show that the induction and reduction of pheromonal activity is relatively rapid that this activity is dependent on the androgen state of the male and that with androgen stimulation females are capable of pheromone production. Total urine protein levels are correlated with pheromonal activity but pheromonal activity is not a function of total protein concentration in the urine. The androgen control of this system may have significant implications in regulating its function in rodent populations.(AUTHORS MODIFIED)

Characterization of the androgen receptor in the skeletal muscle op the rat

Skeletal muscle homogenate of prepuberal, adult uncastrated or short-(1–4days) or long-term (20days) castrated male and female rats was incubated at 0°C with highly labeled ( 3H)5α-dihydrotestosterone (1) or ( 3H) testosterone. After incubation bound and free hormone in the 100,000 g cytosol were separated by agargel electrophoresis at low temperature. Furthermore, the percentage distribution of the main metabolites found in the cytosol was analyzed by thin-layer chromatography. Two androgen binding proteins could be found: One with high affinity (apparent dissociation constant (K d) = 1.4–6.4 × 10 −9M) low capacity (receptor), the other with relative low affinity high capacity. The physico-chemical characteristics of the androgen receptor in the rat skeletal muscle cytosol are similar if not identical to those which have been described for the androgen receptor in the prostate and other androgen dependent organs. However, the amount of available 5α-DHT-binding sites in the skeletal muscle is about 60 times and 7 times lower than in the prostate and bulbocavernosus/levator ani muscle, respectively. No essential androgen metabolism occurs in vitro at 0°C in the skeletal muscle.

In vitro metabolism of testosterone-4-14 C by canine salivary glands.

Testosterone-4-14C (2430 pmol, 0.48 muM) was incubated aerobically in 67 mM phosphate buffer pH 7.4 with homogenates and minces of salivary glands from male dogs. Extracted radiosteroids were resolved by thin-layer chromatography on silica gel, removed and quantitated. Substantially higher NAD+-dependent 17beta-hydroxy-C19-steroid oxidoreductase activity was found in submaxillary gland homogenates than in similar parotid-gland preparations. Preliminary evidence is presented that the enzyme activity per unit wet weight of the minced submaxillary gland is decreased in the 2-week male castrate, in the absence of any recognizable histologic changes in the gland. Testosterone metabolism by canine salivary glands is thus oxidative, contrasting with the reductive 17 beta-hydroxysteroid pathway characteristic of androgen-dependent organs such as the prostate, and is more extensive than in this accessory sex tissue. Our findings suggest that the canine salivary glands are not target organs for circulating male hormone.

Mechanism of action of α-chlorhydrin on the testes and caput epididymidis of rat, gerbil &lt;i&gt;(Meriones hurrianae) &lt;/i&gt; bat and mouse

Chronic administration of alpha-chlorhydrin caused lesions of rat, gerbil and bat testicles selectively. The seminiferous epithelium became systematically depleted of spermatogenic elements. alpha-Chlorhydrin did not produce lesion of the caput epididymidis. Sloughing of the epithelial lining did not occur. No obstruction of the lumen of the epididymal duct was seen. The growth of androgen-dependent organs, i.e. seminal vesicles, epididymis and levator ani muscles was suppressed. alpha-Chlorhydrin caused no response directly on the epididymides. Subcutaneous or oral administration of alpha-chlorhydrin for a period of 3-5 weeks caused no response in the testes and epididymides of the mouse.

Observations on the effects of α-chlorhydrin on the tested and pituitary gonadotrophs of gerbil (&lt;i&gt;Meriones hurrianae&lt;/i&gt;) and rat

(1) Lower doses of alpha-chlorhydrin caused high selectivity of lesions in the seminiferous tubule of rat and gerbil. (2) The seminiferous epithelium became systematically depleted of spermatogonia, spermatocytes, spermatids and finally spermatozoa in this sequence. (3) The suppression of RNA concentration in the testes and seminal vesicle is conspicuous. (4) The growth of androgen-dependent organs, i.e. seminal vesicles, ventral prostate, epididymes and perineal complex, is suppressed. (5) These effects are reversible. Repopulation of testis tubules occurs followed by a 40-day recovery period in rat and gerbil. (6) alpha-Chlorhydrin administration brings about hypertrophy of pituitary gonadotrophs which is also reflected in the increased basophilic cell percentage (control: 15.5% alpha-chlorhydrin: 21.5%; p less than 0.01).