Testosterone metabolites do not participate in the control of hypothalamic LH-releasing hormone

To determine whether the ability of testosterone to increase intrahypothalamic LH-releasing hormone (LHRH) in orchidectomized rats might be explained by the conversion of the hormone into either its 5 alpha-reduced or oestrogenic metabolites, testosterone, 5 alpha-androstan-17 beta-ol-3-one (DHT), 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) and 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol) (2 mg/rat per day for 6 days) and oestradiol (0.1, 0.5, 1.0 and 5.0 micrograms/rat per day for 6 days) were injected into castrated male rats. After 6 days the rats were killed and serum LH levels and intrahypothalamic LHRH stores measured using specific radioimmunoassay procedures. Testosterone and its 5 alpha-reduced metabolites were used in either the free alcohol or the propionate form (dipropionates in the case of the diols); oestradiol was used as oestradiol-17 beta or in the benzoate form. Treatment with testosterone, DHT, 3 alpha-diol and 3 beta-diol resulted in a significant decrease in serum LH levels; all the 5 alpha-reduced testosterone derivatives were more effective than testosterone in this respect. Testosterone and DHT propionates suppressed LH release following orchidectomy totally; 3 alpha-diol and 3 beta-diol dipropionates were less effective. Testosterone increased intrahypothalamic LHRH stores, this effect being much higher after testosterone propionate, i.e. when intrahypothalamic LHRH stores were restored to pre-castration levels. None of the 5 alpha-reduced steroids was capable of modifying the low intrahypothalamic levels of LHRH found following orchidectomy; only 3 alpha-diol dipropionate exhibited some activity, but this was much lower than that of testosterone propionate. Oestradiol-17 beta was totally ineffective in decreasing serum LH in orchidectomized animals; in contrast, oestradiol benzoate progressively decreased serum LH.(ABSTRACT TRUNCATED AT 250 WORDS)     

Steroid metabolism in normal mammary gland and in the dimethylbenzanthracene-induced mammary tumor of rats.

After incubation of [4-14C]progesterone with cell-free homogenates of 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced mammary tumor of rats, 20 alpha-hydroxy-4-pregnen-3-one, 5 alpha-pregnane-3,20-dione, 20 alpha-hydroxy-5 alpha-pregnan-3-one, 3 alpha-hydroxy-5 alpha-pregnan-20-one, and 5 alpha-pregnane-3 alpha, 20 alpha-diol were identified as the metabolites. In normal mammary tissue, however, 4-pregnene-3 alpha-diol was isolated in addition to 5 alpha-reduced, and 3 alpha- and 20 alpha-hydroxy metabolites. When radioactive testosterone was employed as a substrate, 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol were obtained as the metabolites of the mammary tumor. In the normal mammary gland, only 4-andorstene 3 alpha, 17 beta-diol was formed as its metabolite. Although the enzyme activities relevant to the metabolism varied among the tumor examined, the activity of 20 alpha-hydroxysteroid dehydrogenase in the mammary tumor was significantly lower than that in the normal mammary gland, whereas the activity of 5 alpha-reductase was higher in some of the mammary tumors than in the normal gland. The 5 alpha-reductase activity in the normal mammary gland was mostly localized in the crude microsomal fraction, whereas the same enzyme activity in the tumor was detected in all the organelle fractions. The activities of 20 alpha-hydroxysteroid dehydrogenase and NADPH-linked 3 alpha-hydroxysteroid dehydrogenase were found mainly in the cytosol fractions of the tumor and the normal tissue. The NADH-linked 3 alpha-hydroxysteroid dehydrogenase activity was detected only in the cytosol fraction of the normal mammary gland, but in the tumor studied, the activity of this enzyme was detected in all the subcellular fractions examined.     

Seasonal variations of androgens, estrogens, and progesterone in the different lobules of the testis and in the plasma of Salamandra salamandra

Progesterone, 4-androstenedione, testosterone, dihydrotestosterone, 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol), 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol), estrone, and estradiol levels were determined by radioimmunoassay in the different lobules of the testis of Salamandra salamandra throughout the year according to the seasonal cycle. 3 beta-diol levels were not detectable. High levels of steroids were found in the grandular tissue (enlarged pericystic cells after spermiation) and large variations were showed for progesterone, 4-androstenedione, testosterone, 3 alpha-diol, and estrone. In the mature lobule (formed by cysts with mature spermatozoa), only testosterone showed seasonal variations and in the immature lobule (with early stages of meiosis), 3 alpha-diol showed fluctuations. The major estrogen found in the testis of Salamandra was estrone; estradiol stayed at a low level throughout the cycle. The steroids fluctuation seems to be related to the histological evolution of the testis throughout the cycle. The present data were the first on steroid seasonal variations in the testis of an urodele.     

Sexual differences in the Japanese quail: behavior, morphology, and intracellular metabolism of testosterone

Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first experiment, a series of dose-response curves in which length of Silastic testosterone implants was related to effects on several behavioral and physiological variables was established. In Experiment 2, adult males and females were assigned to six experimental groups: intact males and females (I-males and I-females), castrated males and females implanted subcutaneously with 40-mm Silastic implants of T (T-males and T-females), and castrated males and females without hormone treatment (CX-males and CX-females). No CX-bird (male or female) and no I-female exhibited male sexual behavior. However, I-males and T-males regularly copulated during the behavioral tests. No crowing was ever heard in CX-animals and I-females. T-females crowed less than T-males and their crowing sounded weaker than those of males. The cloacal glands of T-females were less developed than those of males. Radioimmunoassay of T and 5 alpha-DHT showed that T-males and T-females have similar plasma levels of androgens. No striking differences were observed in the way testosterone is metabolized by the pituitary gland and central nervous tissues of males and females. By contrast, the production of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha, 3 alpha-diol) was higher in the cloacal glands of males than in those of females. These sex differences were not detected between T-males and T-females. In experiment 3, the cloacal gland of males produced more 5 alpha-reduced metabolites than those of females. The pituitary gland of females also produced more 5 beta-androstane-3 alpha, 17 beta-diol (5 beta, 3 alpha-diol). In syringeal muscles, the production of 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta, 3 alpha-diol was higher in females compared to males.     

Action of 5 alpha-reduced diols on the uterus of sexually immature rats

The effect of testosterone (T), 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) and 5 alpha-and-rostane-3 beta, 17 beta-diol (3 beta-diol) on the uterus of immature rats was studied in combined with estradiol-17 beta (E2) and separate intraperitoneal administration. Repeated administration of T (100 micrograms per 100 g of body mass) caused no changes in the uterine mass whereas a similar dose of 3 alpha-diol resulted in a noticeable effect (0.05 greater than greater than p less than 0.1). 3 beta-diol administered repeatedly at a dose of 1.00 microgram per 100 g of body mass, produced the same uterotropic effect like E2. In combined administration of the above androgens (100 micrograms) and E2 (10 micrograms) 3 alpha-diol only inhibited the uterotropic effect of E2.     

Induction of progesterone receptor by androgens in the mouse uterus

The comparative abilities of 3 naturally occurring androgens to compete for [3H]estradiol-17 beta ([3H]E2)-binding sites in uterine cytosol and to induce uterotrophic responses in immature female mice have been investigated. 5 alpha-Androstane-3 beta,17 beta-diol (3 beta-diol), 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) and 5-androstene-3 beta,17 beta-diol (delta 5-diol) are all effective at diminishing cytoplasmic [3H]E2 binding. Their relative effectiveness are in the order of 3 beta-diol greater than delta 5-diol = 3 alpha-diol. When these steroids were injected intramuscularly (two 100-200 micrograms injections) into immature female mice (21 days old), they induced similar elevations of uterine dry weight, water content, cytosolic estrogen (ER) and progesterone (PR) receptor contents, and nuclear ER content as did estradiol-17 beta (E2). 3 beta-Diol was the most effective steroid at inducing cytosolic and nuclear ER, and PR production in mouse uterus. Followed in effectiveness was delta 5-diol and 3 alpha-diol. Unexpectedly, 3 beta-diol was found to be more potent than E2 in stimulating uterine ER and PR increases. Nonetheless, the androgens are poorer stimulators of uterine dry weight increase and water retention than E2 is. These results indicate that the androgens may interact with the ER system in the uterus to bring about the uterotrophic responses and 3 beta-diol is a more estrogenic steroid than delta 5-diol and 3 alpha-diol in the mouse uterus.     

Oestradiol synergizes with 5 alpha-dihydrotestosterone or 3 alpha- but not 3 beta-androstanediol in inducing sexual behaviour in castrated rats

Castrated male rats were treated with constant-release implants filled with testosterone, oestradiol-17 beta, 17 beta-hydroxy-5 alpha-androstan-3-one (5 alpha-dihydrotestosterone; DHT), 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-Adiol) or 5 alpha-androstane-3 beta,17 beta-diol (3 beta-Adiol). Only testosterone activated the sexual behaviour of the rats. If combined with oestradiol, DHT or 3 alpha-Adiol induced the behaviour, but 3 beta-Adiol failed to have this effect. Oestradiol inhibited the in-vitro formation of [14C]Adiols from [14C]DHT by combined preoptic and hypothalamic tissue, but only when given in high doses. No effect on the formation of [14C]Adiols from [14C]DHT was found in rats treated in vivo with DHT or with the combination of DHT and oestradiol which effectively stimulated sexual behaviour. These results do not support the suggestion that oestradiol may synergize with androgens to induce sexual behaviour in castrated rats by inhibiting androgen metabolism.     

Androgen biosynthetic pathways in the human prostate

It is well recognized that there are two androgens, namely testosterone (T) and dihydrotestosterone (DHT); T plays an important role in the testis and muscle, and DHT is crucial for the development, function and pathology of the prostate. It is generally thought that DHT is produced from the 5alpha-reduction of circulating T before being inactivated by 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) that converts DHT into 5alpha-androstane-3alpha,17beta-diol (3alpha-diol). However, the presence of various steroidogenic enzymes in the prostate as well as the availability at high levels of various steroid precursors such as dehydroepiandrosterone sulphate (DHEAS), dehydroepiandrosterone (DHEA) and 4-androstenedione (4-dione) strongly suggest the existence of additional pathways involved in the biosynthesis and metabolism of DHT. Because steroidogenesis could be different in different species, data from the literature obtained from various human, dog, rat and mouse prostate tissues, as well as primary cells and prostatic cancer cell lines, provide a somewhat confusing picture. In the present chapter, we review the data in order to provide a clearer picture of the pathways involved in DHT biosynthesis and metabolism in the human prostate.     

Interactions of an anti-androgen (cyproterone acetate) with the androgen receptor system and its biological action in the rat ventral prostate

Male Wistar rats were castrated and implantated with testosterone-filled silastic depots (in vitro release rate: 60 micrograms/24 h) prior to treatment with 10 mg cyproterone acetate (CyAc) on day 1, and 5 mg on days 4, 7, 10 and 13. Animals were sacrificed on day 14. Control animals were treated identically, with the exception of CyAc administration. Blood was collected and the ventral prostates of 6-8 animals were pooled, homogenized and processed into cytosol and purified nuclei. Steroid determinations (CyAc, testosterone, 5 alpha-dihydrotestosterone (DHT), 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol)) were performed by RIA. Specifically bound DHT (charcoal resistant DHT = CR-DHT) represents DHT values (RIA) following treatment of cytosol or nuclear extract with dextran coated charcoal. The androgen receptor was determined in cytosol and nuclear extract by 'exchange assay' using [3H]methyltrienolone (MT) (18 h, 15 degrees C). The main results were: 1) The steroid levels in plasma (testosterone, DHT, 3 alpha-diol) were in the range of untreated adult animals and not significantly influenced by the CyAc treatment. Final CyAc levels were 305 +/- 58 nmol/l (mean +/- SD, n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)     

Altered metabolism of androgens in elderly men with benign prostatic hyperplasia.

Kinetics of testosterone, dihydrotestosterone (DHT) and 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) were studied in 7 elderly healthy men (ages 61 to 80 years) with benign prostatic hyperplasia (BPH). Clearance rates were determined by the constant infusion technique with labeled testosterone and DHT. Metabolic clearance rate (MCR), conversion ratio (CR), the transfer constants (rho) and production rates (PB) were calculated. Plasma androgens were measured by specific radioimmunoassay. Plasma testosterone was 516 +/- 314 (SD) ng/dl, plasma DHT was 74.6 +/- 19.6 (SD) ng/dl and plasma 3alpha-diol was 16.4 +/- 4.1 (SD) ng/dl. An elevated DHT level in elderly men with BPH wasconfirmed. MCRT was 620 +/- 65 (SD) liter/day and MCRDHT was 393 +/- 50 (SD) liter/day. Both MCRT and MCRDHT in elderly men were significantly lower than in young men. PBT was 3.2 +/- 2.1 (SD) mg/day and PBDHT was 291 +/- 87 (SD)migrogram/day. PBDHT was the same in elderly and young men. DHT production is maintained in elderly men despite reduction of testosterone production. From the data, it was claculated that in contrast to young men where greater than 80% of blood DHT is from secreted testosterone, over 50% in elderly men is derived from secretion or production of DHT by the testis or even more likely the prostate.     

Hormone blood levels and their inter-relationships in normal men and men with benign prostatic hyperplasia (BPH).

In 128 non-hospitalized men (age range 36-65 years) rectal palpation revealed in 54 cases an enlargement of the prostate (group II), which was very distinct in 20 cases (group III). The measurement of testosterone (T), 5alpha-dihydrotestosterone (DHT), 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) oestradiol (Oe2), sex-hormone-binding-globulin binding capacity (SHBG), luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (Prl) in the blood of normal men (group I) and those with BPH (group II or III) demonstrated no significant differences between the three groups when respective age ranges were compared. A significant increase of FSH and decrease of 3alpha-diol with age was seen in the normal group (I), which was similar but less pronounced in BPH (groups II and III). A distinct increase of DHT with age was found in BPH (group II), which was not so dominant in normal men (group I). From these data it is concluded that the conversion of DHT to 3alpha-diol might be reduced in older males independent from the occurrence of BPH and that the hyperplastic prostate possibly secretes significant amounts of DHT into the circulation. These results are discussed with respect to their possible role in the pathogenesis of BPH.     

Prostate formation in a marsupial is mediated by the testicular androgen 5 alpha-androstane-3 alpha,17 beta-diol

Development of the male urogenital tract in mammals is mediated by testicular androgens. It has been tacitly assumed that testosterone acts through its intracellular metabolite dihydrotestosterone (DHT) to mediate this process, but levels of these androgens are not sexually dimorphic in plasma at the time of prostate development. Here we show that the 3 alpha-reduced derivative of DHT, 5 alpha-androstane-3 alpha,17 beta-diol (5 alpha-adiol), is formed in testes of tammar wallaby pouch young and is higher in male than in female plasma in this species during early sexual differentiation. Administration of 5 alpha-adiol caused formation of prostatic buds in female wallaby pouch young, and in tissue minces of urogenital sinus and urogenital tubercle radioactive 5 alpha-adiol was converted to DHT, suggesting that circulating 5 alpha-adiol acts through DHT in target tissues. We conclude that circulating 5 alpha-adiol is a key hormone in male development.     

Effect of experimental alterations in serum levels of 5 alpha-androstane-3 beta,17 beta-diol on the timing of puberty in the female rat

It has been suggested that in the rat, 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) is physiologically involved in restraining the onset of female puberty. To test this hypothesis several experiments were performed. In normal rats, serum levels of 3 alpha-diol decline slightly during the initial phases of puberty and then sharply several hours before the afternoon preovulatory LH surge on the day of first proestrus. Inhibition of 5 alpha-reductase activity with a highly specific inhibitor, 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstane-3-one (4-MA) strikingly depressed both ovarian content and serum levels of 3 alpha-diol, but failed to advance vaginal opening or first ovulation. Administration of different doses of 3 alpha-diol to juvenile rats via Silastic capsules produced a dose-related increase in serum 3 alpha-diol levels. Titers attained ranged from values similar to those of untreated juvenile rats to levels more than 10-fold higher. None of the concentrations, however, inhibited the LH surge and ovulation induced by pregnant mare serum gonadotropin (PMSG). When a similar treatment was administered to normally maturing rats, only the high dose of 3 alpha-diol delayed the age of vaginal opening and of first ovulation. Serum 3 alpha-diol levels attained with this dose were markedly higher than those of untreated juvenile rats (1,086 +/- 267 vs. 124 +/- 14 pg/ml, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies on the feedback regulation of gonadotropin concentrations in male rats. (II). Partial characterization of 5 alpha-reductase in the medial basal hypothalamus and anterior pituitary gland

To evaluate the testosterone (T) 5 alpha-reductase activity in medial basal hypothalamus (MBH) and anterior pituitary gland of the adult male rat, whole homogenate of MBH or anterior pituitary glands was incubated with 14C-T in the presence of coenzymes under various experimental conditions. Major metabolites were 5 alpha-dihydrotestosterone (DHT), 5 alpha-androstane-3 alpha (beta), 17 beta-diol(3 alpha(beta)-diol) and delta 4 androstenedione. The activity of 5 alpha-reductase was expressed as the sum of the amount of DHT and 3 alpha(beta)-diol formed after incubation. The metabolites converted from T was separated and identified by thin layer chromatography and confirmed by recrystallization. The anterior pituitary gland possessed about four times higher 5 alpha-reductase activity compared with that in MBH. NADPH was essential for 5 alpha-reductase activity. They existed in microsomal fraction. They had same optimum temperature and almost same optimum pH. The Michaelis constant of the 5 alpha-reductase for T in MBH and anterior pituitary gland was 3.1 X 10(-7) M and 5.6 X 10(-7) M, respectively. These results suggest that 5 alpha-reduced metabolites of T, especially DHT have some physiologically significant roles in not only MBH but also anterior pituitary gland. Furthermore, it is noteworthy that 5 alpha-reductase in the anterior pituitary showed higher activity than that in MBH.     

Virilization of the urogenital sinus of the tammar wallaby is not unique to 5alpha-androstane-3alpha,17beta-diol

The androgen 5alpha-androstane-3alpha,17beta-diol (5alpha-adiol) is synthesized in testes and secreted into plasma of male tammar wallaby pouch young and appears to virilize the urogenital sinus. To provide insight into its mechanism of action, a dose response study showed that administration of 1 microg 5alpha-adiol monoenanthate per g body wt. per week for 3 weeks to 24-day-old female pouch young induced prostate bud formation equivalent to that of males of the same age. Administration of this same dose of the enanthates of testosterone, dihydrotestosterone, and 5alpha-adiol to female pouch young caused equivalent virilization of the urogenital sinus. The fact that 5alpha-adiol does not exert a unique effect, together with our earlier findings in this species that 5alpha-adiol and testosterone are converted to dihydrotestosterone in the urogenital sinus and that virilization of the urogenital sinus is prevented by the androgen receptor antagonist flutamide, suggest that 5alpha-adiol is a circulating precursor for dihydrotestosterone formation in this tissue.     

In vivo uptake and metabolism of 3-h-5alpha-androstane-3alpha,17beta-diol and of 3-h-5alpha-androstane-3beta,17beta-diol by human prostatic hypertrophy.

Tritiated 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) and 5alpha-androstane-3beta,17beta-diol (3beta-diol) respectively were administered to patients with benign prostatic hypertrophy (bph) undergoing prostatectomy. In prostate and skeletal muscle homogenates and in plasma the total radioactivity content as well as the formation of metabolites were measured. Histological examination of each ectomized prostate was performed to evaluate the cellular composition of the tissue. After 3alpha-diol injection, a higher uptake of radioactivity in the prostate was obtained than after 3beta-diol. Within 30 min the 3alpha-isomer was very efficiently converted to 5alpha-DHT, while most of the 3beta-isomer remained unchanged. There was, however, also after administration of the 3beta-diol a substantial biconversion to 5alpha-DHT as has been confirmed by recrystallization to constant specific radioactivity. Only after 3beta-diol epiandrosterone was detected in small but significant amounts. 3alpha-diol administration resulted in distinct concentrations of 3beta-diol, whereas the conversion of 3beta-diol to the 3alpha-isomer was insignificant. When comparing the histological composition of the prostatic tissue with the accumulation of radioactivity and the formation of metabolites only a weak correlation between glandular structure and radioactivity uptake after 3alpha-diol administration could be revealed.     

Tissue androgen concentrations in golden hamsters with benign prostatic tumours

Using gas chromatography-high resolution mass spectrometry with selected ion detection, the concentrations of testosterone, 5alpha-dihydrotestosterone, androsterone, 5alpha-androstane-3alpha,17beta-diol, 5alpha-androstane-3beta,17alpha-diol and 5alpha-androstane-3beta,17beta-diol were measured in the dorsal and ventral prostates of two strains of golden hamster (Mesocricetus auratus) at various ages from 60 to 250 days. The tissue concentrations from a control strain were compared with those of the BIO 87.2 strain of hamster, the latter developing benign hyperplasia of the prostate between 90 and 120 days of age. Marked increases in the concentration of total 5alpha-androstanediols in both prostatic lobes of the BIO 87.2 strain were detected, with the highest level of over 345 nmol/g protein being found at 200 days of age. In comparison, the control strain showed a less pronounced increase in concentration at 150 days. Increases in total 5alpha-androstanediols were mainly associated with increases in the concentration of 5alpha-androstane-3alpha,17beta-diol. Concentrations of testosterone in prostatic tissue were also found to increase in the BIO 87.2 animals with peak values being seen at 200 days. Increases in concentration of androsterone were observed by 150 days and these levels were maintained up to 250 days of age. Control animals showed no comparable increases in testosterone and androsterone during the time-course studied. Surprisingly, no significant variation in 5alpha-dihydrotestosterone concentration was detected in either strain from 60 to 250 days although levels were slightly but consistently higher in the BIO 87.2 strain. There were no significant fluctuations in any of the androgens assayed either before or during tumour development. The increases in 5alpha-androstane-3alpha,17beta-diol, testosterone and androsterone were detected only after tumours had become established.     

Plasma concentrations of ovarian steroids in the freshwater European silver eel (Anguilla anguilla L.): effects of hypophysectomy and transfer to sea water

Intact and hypophysectomized freshwater (FW) silver eels were transferred to tanks of FW or artificial sea water (SW; salinity = 0.60 osmol/l) which were simultaneously renewed twice a week. Fish were killed 2 months after transfer and plasma was assayed for ovarian steroids. In all fish, 5 alpha-androstane-3 beta,17 beta-diol was present, while 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha,17 beta-diol were undetectable. In intact FW eels, plasma levels of testosterone, 5 alpha-androstane-3 beta,17 beta-diol and oestradiol-17 beta were approximately 0.15 nmol/l. In intact SW eels, no change in plasma levels of testosterone and 5 alpha-androstane-3 beta,17 beta-diol was found, whereas the concentration of oestradiol-17 beta was increased significantly (P less than 0.01), indicating stimulation of aromatase activity. In hypophysectomized compared with intact FW fish, plasma levels of testosterone and 5 alpha-androstane-3 beta,17 beta-diol were decreased (P less than 0.05) and there was a slight but significant (P less than 0.01) augmentation of the plasma concentration of oestradiol-17 beta which may have involved the removal of pituitary-dependent inhibition of aromatase activity, possibly by 5 alpha-reduced compounds. In hypophysectomized compared with intact SW fish, plasma levels of testosterone, 5 alpha-androstane-3 beta,17 beta-diol and oestradiol-17 beta were decreased (P less than 0.05); in the case of oestradiol-17 beta, this may have reflected the diminished ovarian synthesis of testosterone, its precursor. The plasma level of oestradiol-17 beta was, however, higher in SW than in FW fish, even in hypophysectomized eels. This suggests that extra-pituitary mechanisms mediate, at least partly, the effects of transfer to SW on aromatase activity.     

Metabolism of C19 steroids in vitro by the submaxillary salivary gland of mature and immature domestic pigs

Homogenates of the submaxillary glands of immature and mature pigs were incubated with 3H-labelled C19 steroids which have been shown previously to be metabolized in vitro by the submaxillary gland of mature boars. Dehydroepiandrosterone was metabolized largely to androstenedione, 5 alpha-androstane-3,17-dione and androsterone, and to small amounts of testosterone, 5 alpha-dihydrotestosterone and 5 alpha-androstanediols. Testosterone yielded predominantly 5 alpha-androstane-3 alpha, 17 beta-diol with smaller amounts of other 5 alpha-reduced products, i.e. 5 alpha-dihydrotestosterone, 5 alpha-androstane-3 beta, 17 beta-diol, 5 alpha-androstane-3,17-dione and androsterone; 5 alpha-dihydrotestosterone and the two epimeric 5 alpha-androstane-3 alpha/3 beta, 17 beta-diols were interconverted. These and earlier results show that the porcine submaxillary gland has the capacity in vitro to metabolize selected C19 steroids in a way which is not related to either sexual maturity or sex of the animal; in this respect the findings support certain aspects of previous histochemical studies.     

Studies on the feedback regulation of gonadotropin concentrations in male rats. (III). The effects of testosterone and its metabolites on gonadotropin secretion from rat pituitary cells in culture

To determine whether dihydrotestosterone (DHT) or estradiol (E2) exerts negative or positive feedback effects on rat pituitary gland, Testosterone (T) metabolite (T, DHT, 5 alpha-androstane-3 alpha, 17 beta-diol:3 alpha-diol or E2) was added to the cultured pituitary cells. Anterior pituitary glands were obtained from 6-week-old male rats. Pituitary cells were prepared by trypsin digestion and incubated with various concentrations of steroid hormones for 72 h to determine the effects of steroid hormones on basal secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH) after 48 h preculture without steroids. Then 10 nM luteinizing hormone-releasing hormone (LH-RH) with appropriate concentrations of these steroid hormones was added to the pituitary cells in culture and incubated for another 6h to determine the effects of steroid hormones on LH-RH induced gonadotropin release. After the incubation, pituitary cells were lysed with 0.1% Triton X100 to measure the intracellular gonadotropin content. The concentration of LH and FSH was determined by radioimmunoassay. T, DHT and 3 alpha-diol stimulated basal FSH but not basal LH secretion, and inhibited both the release of FSH and LH from cultured pituitary cells during incubations with LH-RH in a dose-dependent fashion. Intracellular content of both FSH and LH were increased, and total FSH and not LH was also increased by the addition of DHT in a dose-dependent manner. E2 did not exert any of such effects on pituitary cells in culture. These studies suggest that 5 alpha-reduced metabolites but not aromatized metabolite of T play an important role on feedback regulation of gonadotropin secretion at pituitary level. DHT directly acts on pituitary gland not only to stimulate the production of FSH but also to suppress FSH and LH secretion induced by LH-RH.