Quantitative assessment of the biological effects of follicle regulatory protein on dihydrotestosterone-maintained spermatogenesis in hypophysectomized rat.

Follicle regulatory protein (FRP) isolated from porcine ovarian follicles influences folliculogenesis through a paracrine mechanism. A similar protein has been found in the testes and seems to have some inhibitory effects on spermatogenesis when administered to intact male experimental animals. On the basis of female and male studies, it has been ascertained that the effects of FRP are at the level of gonads and not the pituitary or the hypothalamus. In the studies with intact males it was not possible to determine the exact site of FRP action on the testes. Dihydrotestosterone (DHT) has been shown to maintain spermatogenesis in hypophysectomized rats. In order to determine if the inhibitory effects of FRP are at steps prior to the formation of DHT, FRP was administered to hypophysectomized rats that were injected with DHT. Groups of adult rats were hypophysectomized and treated daily with FRP, DHT, FRP + DHT, or vehicle alone for 30 days. At necropsy, body, testes, prostate glands, and seminal vesicle weights were recorded. One testis and sexual accessory glands were fixed for histological evaluation. The contralateral testis was decapsulated, six 2 mm segments of seminiferous tubules, representing defined stages of spermatogenesis, were isolated by transillumination-assisted microdissection, and spermatogenic cells were quantified by DNA flow cytometry. Histologically, the seminiferous tubules of vehicle-treated hypophysectomized controls showed advanced regression. Rats treated with FRP alone showed similar degeneration. On the other hand, rats treated with DHT showed maintenance of spermatogenesis comparable to normal controls. The testes of rats treated with FRP + DHT were indistinguishable from those treated with DHT only. Flow cytometric quantification of germinal cells from all groups confirmed the histological findings. In this study FRP did not exert deleterious effects on DHT-maintained spermatogenesis. This finding suggests that the inhibitory effects of FRP on spermatogenesis in intact animals may not be a direct effect on spermatogenic cells but may impair androgen action or production or DHT formation.

Hair loss. What causes it and what can be done about it.

Although both men and women throughout history have seen hair as an important aspect of appearance, it is especially important today, in light of the great emphasis on youthfulness. A new interest in preventing baldness has been stimulated recently by the publicity given to certain products now under investigation that have shown an ability to retard or reverse male pattern baldness in certain individuals. Hair loss has many possible causes, such as systemic diseases, infections, toxic agents, and hormone imbalances. Treatment of the underlying disorder alleviates the shedding of hair. Balding may also be a normal physiologic occurrence in women taking oral contraceptives or after parturition and in men with male pattern baldness. The latter can be treated topically with progesterone or minoxidil. Minoxidil has been studied extensively and has been shown to improve balding at the vertex of the scalp, particularly in young men who have only begun to lose hair. Cases of more extensive male pattern baldness and baldness secondary to scarring can be treated effectively with surgical procedures.

5 alpha-dihydrotestosterone formation is necessary for embryogenesis of the rat prostate.

To determine the role of 5 alpha-dihydrotestosterone (DHT; 17 beta-hydroxy-5 alpha-androstan-3-one) in formation of the embryonic prostate, we quantitated prostatic development in urogenital tracts of control male newborn and offspring of rats treated with a specific 5 alpha-reductase inhibitor (L652,931; Merck, Sharp, and Dohme) during prostate morphogenesis. Treatment with the 5 alpha-reductase inhibitor (50 mg/kg.day) from days 14-22 of gestation impaired development of the prostate and virilization of the external genitalia in male offspring compared to those in control animals. However, virilization of the internal genitalia (seminal vesicles, epididymis) was unaffected. Simultaneous administration of DHT (50 mg/kg.day) with the 5 alpha-reductase inhibitor restored prostate development and anogenital distances of males to normal and virilized the external genitalia of females. We conclude that DHT is the active androgen responsible for prostatic development in the rat.

Androgen-dependent human prostate cancer in nude mice. The PC-82 tumor model.

Permanent transplantable human tumors in nude mice offer the possibility of studying the impact of different (endocrine) treatment regimens on human cancer tissue. Among the limited number of human tumor models in athymic nude mice developed so far, the PC-82 tumor (which was established in our institution) mimics many of the important properties of clinical prostate cancer. The absence of PC-82 tumor growth in intact female and in castrated male mice indicates the absolute requirement of androgen for the growth of this tumor. Delayed testosterone (T) substitution (up to 70 days after tumor grafting) in PC-82 transplanted female mice resulted in tumor growth. This indicated that after androgen withdrawal at least part of the cells do not die and keep the capability to respond to androgens. Androgen withdrawal from T-implanted tumor-bearing female mice caused a rapid reduction (90% within 1 day) of the tissue T and a slower decline (up to 90% within 7-10 days) of tissue DHT concentrations. By the use of Silastic implants, containing different proportions of T mixed with cholesterol, circulating T levels of 0.2-20 nmol/L were obtained. It was observed that a constant plasma T level between 1 and 2 nmol/L (achieved with 10% T implants) is the threshold below which growth of the PC-82 tumor tissue is no longer stimulated.

The influence of castration on the development of prostatic carcinoma in the dog. 43 cases (1978-1985).

Prostatic carcinoma (PC) was diagnosed in 43 dogs at the Michigan State University Veterinary Clinical Center (MSU-VCC) between 1978 and 1985. Of the 43 dogs with histologically confirmed PC, 19 (44.19%) had been castrated at least three years prior to the development of any prostatic disease. Seven of the castrates had been neutered at less than 12 months of age. Fourteen dogs (32.55%) were presented as intact males at the time of diagnosis. The remaining ten dogs (23.62%) had been castrated as treatment for presumptive prostatic disease prior to referral to the MSU-VCC. Dates of castration were known in all cases. In this study, therefore, castration at any age showed no sparing effect on the risk of development of PC in the dog. The etiology of PC in the dog may not be exclusively related to testicular hormones. Work in humans suggests that the adrenal and pituitary glands play a significant role in the disease. Preliminary work in dogs supports that nontesticular androgens exert a significant influence on the canine prostate.

Androstenedione may be a more important precursor of tissue dihydrotestosterone than testosterone in women.

The expression of androgenic features in the external genitalia and skin is largely dependent on the intracellular formation of dihydrotestosterone (DHT). The relative contributions of androstenedione (delta 4A) and testosterone (T) to DHT production in skin have not been compared. To clarify this, the authors studied the in vitro conversion of delta 4A to DHT, delta 4A to T, and T to DHT in genital and/or pubic skin minces from 20 normal women, 4 hirsute women, and 3 normal men. In normal women, the mean conversion ratios (CRs) of delta 4A to DHT in genital skin (7.06% +/- 1.72%, standard error of the mean) and in pubic skin (2.30% +/- 0.26%) were both significantly higher (P less than 0.05) than the respective mean CRs for T to DHT in genital and pubic skin (3.53% +/- 0.68% and 0.74% +/- 0.14%). In hirsute patients, the data suggested a higher CR of delta 4A to DHT (10.6% +/- 4.59%) compared with T to DHT (4.17 +/- 1.07). Conversely, the CR of delta 4A to DHT (12.8% +/- 9.8%) was significantly lower than the CR of T to DHT (59.7% +/- 12.0%) in male genital skin (P less than 0.01). Since daily blood production rates and serum concentrations of delta 4A are higher than T in women, it is concluded that delta 4A may be a more important precursor for DHT in female skin.

Androgenic regulation of luteinizing hormone secretion: relationship to androgen binding in sheep pituitary.

Castrated ram lambs (wethers) were investigated for sensitivity to androgen feedback and to determine whether this feedback inhibition of luteinizing hormone (LH) was associated with changes in pituitary androgen receptors. Administration of Silastic capsules containing either dihydrotestosterone or testosterone was found to produce dose-dependent inhibitory effects on serum LH levels in wethers. Physiological dosages of these androgens (i.e., those that produce serum levels of dihydrotestosterone [0.24 ng/ml] or testosterone [2.1 ng/ml] similar to those of intact rams) resulted in differential inhibition of serum LH and LH content of the anterior pituitary. Whereas the inhibitory effect of dihydrotestosterone on pituitary LH content was much more dramatic than that seen with testosterone, the high dosage of testosterone also produced a substantial decrease in pituitary LH content. Responses of the pituitary to changes in serum androgen were compared to responses of the seminal vesicle, which served as a control androgen target organ. Androgen levels were positively correlated with seminal vesicle weights, but pituitary weights were unaffected by castration and/or androgen replacement. Treatments with dihydrotestosterone were associated with decreased cytosol androgen binding activity (i.e., receptors) in pituitary and seminal vesicle, suggesting that both of these tissues were sites of androgen action. Although testosterone inhibited serum LH levels, pituitary cytosol androgen receptors were not affected by changes in serum testosterone. We conclude from these data that dihydrotestosterone is a physiological regulator of pituitary LH secretion in the ram and that further study is needed to investigate the complex actions of testosterone and its metabolites on pituitary function.

Effect of prolactin and androgens on the prostate of bonnet monkeys, Macaca radiata: I. Nucleic acids, phosphatases, and citric acid.

The effects of prolactin (PRL), bromocriptine (Br), testosterone propionate (TP), dihydrotestosterone (DHT), and the combinations of these androgens with PRL/Br on the growth and secretory activities of cranial and caudal prostates were studied in castrated mature monkeys, Macaca radiata. Castration decreased the body weight, organ weights, nucleic acids (DNA and RNA), phosphatases, and citric acid of cranial and caudal prostates. PRL did not alter the body weight but increased the organ weights, nucleic acids, phosphatase activities, and citric acid. Br given alone decreased the body weight and the secretory activities of prostates but caused no significant alteration in the nucleic acids. TP/DHT replacement brought back the body weight and prostatic nucleic acids to normal. It enhanced the weights, phosphatase activities, and citric acid contents of cranial and caudal prostates. PRL + TP/DHT enhanced the body weight, organ weight, and secretory activities. Br + TP/DHT decreased the body weight and secretory products of prostate but it did not produce any alteration in the organ weight and RNA content. These results suggest that PRL plays a specific stimulatory influence on monkey prostate.

Sex hormones and cognitive functioning in men.

Blood and saliva samples were obtained from 117 healthy young men, following which radioimmunoassays were used to determine the serum concentrations of testosterone (Tser), 5 alpha-dihydrotestosterone (DHT), and the level of free testosterone (Tsal) in the saliva. The cognitive functioning was determined by five spatial and six verbal ipsative test scores, reflecting intra-individual variance in the performance of these tasks, independent of the person's general level of achievement. Within the normal physiological range of androgen levels--especially Tser and to a lesser extent DHT and Tsal--showed a significantly positive correlation with measures of spatial ability and field dependence-independence and a significantly negative correlation with measures of verbal production.

Effects of androgens and estrogens on the vasopressin and oxytocin innervation of the adult rat brain.

Recently we reported that castration of rats eliminates vasopressin immunoreactivity in the lateral septum and other areas that appear to receive vasopressin innervation from the bed nucleus of the stria terminalis. Testosterone treatment counteracts this effect of castration. In the present study, we investigated whether this action of testosterone depends on its androgenic or estrogenic metabolites by treating long-term castrated rats with estradiol (E) and/or 5 alpha-dihydrotestosterone (DHT) or testosterone. The brains were then processed for immunocytochemistry or radioimmunoassay. DHT did not increase vasopressin staining in the lateral septum, although it fully restored the size of the seminal vesicles. E did restore the original fiber density, but individual fibers stained more weakly than in sham-operated males. Only treatment with both E and DHT fully restored the vasopressin innervation. This pattern was also reflected in the radioimmunoassay data. The vasopressin content of the lateral septum decreased about 90% after castration but was fully restored by either testosterone or E + DHT treatment. E alone, however, was only half as effective as E + DHT. The treatments had no effect on the oxytocin content of the septum, or on the vasopressin or oxytocin content of the dorsal vagal complex. The results suggest that E mediates most of the effects of testosterone on the vasopressin innervation of the lateral septum. DHT enhances the response to E but has little effect on its own.

The differential effects of neonatal androgen, estrogen and progesterone on adult rat prostate growth.

Physiologic surges of serum androgen, estrogen and progesterone normally occur in both rat and human males during the neonatal periods. The effect of these hormone surges on the sex accessory tissues is not known. This study demonstrates that neonatal dihydrotestosterone, 17 beta-estradiol, or progesterone can permanently alter the androgen sensitivity of adult rat sex accessory tissues. Neonatal dihydrotestosterone or progesterone can permanently increase the androgen sensitivity of the adult prostate above normal while neonatal estradiol permanently decreases adult prostate androgen sensitivity below normal. The results of this preliminary study suggest that normally occurring neonatal hormone surges may permanently mark, or imprint, the prostate and determine its future growth in adulthood.

Cellular analyses of hormone influence on motoneuronal development and function.

The striated bulbocavernosus (BC) muscles of the rodent perineum are innervated by motoneurons in the spinal nucleus of the bulbocavernosus (SNB). In adulthood, the BC muscles are present in males only. However, newborn female rats have BC muscles, and SNB cells have made both anatomical and functional contact with them. Nevertheless, both motoneurons and muscles will degenerate unless androgens are administered perinatally. Such androgen treatment appears to be acting primarily on the BC muscles themselves, since the muscles are spared by androgen even after the loss of supraspinal neural afferents or even the entire lumbosacral spinal cord. Furthermore, androgen can spare SNB motoneurons that are themselves androgen insensitive. Perinatal steroid treatments can also alter the final spinal location of SNB cells as determined by retrograde tracing studies. Androgen continues to modify the morphology of the SNB system in adulthood, altering the size of both motoneurons and targets, which may be important for the reproductive function of BC muscles. Finally, the sexually dimorphic character of motoneuronal groups innervating perineal muscles seems to be common in mammals, since the homologue of the SNB, Onuf's nucleus, has more cells in males than in females in both dogs and humans.

Hair follicles and associated glands as androgen targets.

The growth of hair, except that on the scalp, and the secretion of sebum are, in general, under the major influence of androgens. However, the responses of the hair follicles and their associated glands vary greatly between sites and between individuals. On the face, trunk and extremities the most important role of testosterone is to increase the period of activity, the anagen phase, of the hair follicle, though it also increases the rate of growth, thickness, extent of medullation and pigmentation of the hair. These effects involve high levels of hormone and its conversion to 5 alpha-dihydrotestosterone in the target organ. In contrast, the lower pubic triangle develops luxuriantly even in absence of 5 alpha-reductase. In the sebaceous glands, cell replication and lipid synthesis do not seem to be identically controlled, since they respond differently to inhibitors. The response of the sebaceous glands to androgens involves the interaction at the target site of pituitary factors, for which growth hormone, prolactin, and melanocyte stimulating hormone are all putative candidates. The most important scientific and clinical question is whether, in any particular circumstances, the degree of response of the hair follicles or sebaceous glands is determined by the level of available androgen or by the sensitivity of the target organ. While it is true that some patients with hirsutism or acne have above normal levels of plasma androgens or below normal levels of SHBG, a substantial proportion are normal in all respects. Moreover, the rates of hair growth on the extremities or of sebum excretion on the forehead do not seem to be correlated either positively with plasma androgens or negatively with SHBG, though they each have been shown to be correlated with circulating 5 alpha-dihydrotestosterone. The conclusion must be that, although male-type hair growth and high sebaceous secretion may be caused by, or at least accompanied by, high levels of free testosterone, the critical factor is more likely to be the peripheral response.

The dihydrotestosterone (DHT) hypothesis of prostate cancer and its therapeutic implications.

Data are presented showing that human prostatic adenocarcinoma depends on dihydrotestosterone (DHT) and not testosterone (T) for growth. It follows that androgen ablative therapy should be directed toward elimination of DHT with retention of circulating T. This can be achieved by using a 5 alpha-reductase inhibitor such as 6-methyleneprogesterone (6-MP) (VII). Arguments are presented showing that 6-MP (VII) is expected 1) to function as a prophylactic agent against prostate cancer, 2) to represent an attractive therapeutic modality for palliative treatment of the hormone-responsive disease, and 3) to be compatible with other therapeutic modalities when very low prostatic levels of DHT should be within reach.

Nipple differentiation in fetal male rats treated with an inhibitor of the enzyme 5 alpha-reductase: definition of a selective role for dihydrotestosterone.

In the rat, androgens are responsible for sexually dimorphic nipple differentiation. Nipples are expressed in the female, while in the male, the nipple anlage regress prenatally. Mammary gland development is present in both sexes. Treatment of pregnant Sprague-Dawley rats from days 12-21 of gestation with the aza-steroid 17 beta-N,N-diisopropylcarbamoyl-4-aza-5 alpha-androstan-3-one, a competitive inhibitor of the enzyme 5 alpha-reductase, resulted in nipple development in male offspring. Additionally, there was feminization of the external genitalia, with urethral displacement to the base of the phallus. The role of androgens in suppression of nipple anlage in the male rat fetus is known. This study, however, suggests for the first time a selective role for 5 alpha-dihydrotestosterone in regression of the nipple anlage in utero. Thus, 5 alpha-dihydrotestosterone may be critical not only for masculinization of the external genitalia, but also for inhibition of nipple development in the male rat fetus.