Production and effects of 7 alpha-hydroxytestosterone on testosterone and dihydrotestosterone metabolism in rat testis

Metabolomic and transcriptomic responses of mouse testis to the dextran sulfate sodium induced colitis

Inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis, are widespread in developed countries and gradually increasing in developing countries. Evidences showed that man with CD has a decrease of serum testosterone, but how IBD take effects on testicular testosterone synthesis is not well elucidated. To investigate the effects of IBD on testis, we analyzed testicular metabolome and transcriptome data of the dextran sulfate sodium (DSS) induced IBD mice. As a result, metabolomic data showed that DSS indeed induced androgen decrease in mouse testis. Correspondingly, androgen synthesis associated genes, especially Lhcgr, were down-regulated in DSS testis. From the metabolomic data, we found vitamin intake associated metabolites vitamin B2 and pyridoxamine were significantly decreased, whereas fatty acid metabolism associated molecules N-lauroylglycine and N-decanoylglycine were increased in DSS testis. In addition, we found 8-hydroxy-deoxyguanosine, a DNA oxidative damage marker, and 8-oxoguanine, a molecule responsible for DNA damage repair, were also changed in DSS testis. Simultaneously, our data also showed that DSS up-regulated the expression of meiosis initiation associated gene Stra8 and oxygen transport associated genes in testis. In summary, these results depicted the complex effects of colitis on testis. These metabolites and transcripts changed in DSS testis could be used as potential targets for IBD treatment or symptom relieve.

GC-MS-based metabolic signatures reveal comparative steroidogenic pathways between fetal and adult mouse testes

BACKGROUND

Previous studies on gonadal steroidogenesis have not compared metabolic pathways between fetal and adult mouse testes to date.

OBJECTIVES

To evaluate comparative metabolic signatures of testicular steroids between fetus and adult mice using gas chromatography-mass spectrometry (GC-MS)-based steroid profiling.

MATERIALS AND METHODS

GC-MS with molecular-specific scan modes was optimized for selective and sensitive detection of 23 androgens, 7 estrogens, 14 progestogens, and 13 corticoids from mouse testes with a quantification limit of 0.1-5.0 ng/mL and reproducibility (coefficient of variation: 0.3%-19.9%). Based on 26 steroids quantitatively detected in testes, comparative steroid signatures were analyzed for mouse testes of 8 fetuses on embryonic day 16.5 and 8 adults on postnatal days 56-60.

RESULTS

In contrast to large amounts of steroids in adult testes (P < .0002), all testicular levels per weight unit of protein were significantly increased in fetal testes (P < .002, except 6β-hydroxytestosterone of P = .065). Both 11β-hydroxyandrostenedione and 7α-hydroxytestosterone were only measurable in fetal testes, and metabolic ratios of testosterone to androstenediol and androstenedione were also increased in fetal testes (P < .05 for both).

DISCUSSION AND CONCLUSION

Testicular steroid signatures showed that both steroidogenic Δ⁴ and Δ⁵ pathways in the production of testosterone were activated more during prenatal development. Both 7α- and 11β-hydroxylations were predominant, while hydroxylations at C-6, C-15, and C-16 of testosterone and androstenedione were decreased in the fetus. The present GC-MS-based steroid profiling may facilitate understanding of the development of testicular steroidogenesis.

7alpha-hydroxytestosterone affects 1 beta-hydroxysteroid dehydrogenase 1 direction in rat Leydig cells

The cytochrome P450 2A1 (CYP2A1) is a P450 enzyme that catalyzes the metabolism of testosterone. CYP2A1 has been reported to be present in rat testis. However, its developmental changes and function have not been well characterized. The purpose of this study was to measure the abundance of CYP2A1 (Cyp2a1) mRNA in the developing rat testis and Leydig cells and examine the effects of its product, 7 alpha-hydroxytestosterone (7HT), on an important enzyme, 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1) that interconverts active corticosterone and inactive 11-dehydrocorticosterone. As detected by real-time PCR, Cyp2a1 was found to be present exclusively in the Leydig cell. CYP2A1 activity in adult Leydig cells was 5-fold higher than those in progenitor or immature Leydig cells. 7HT competitively suppressed 11 beta-HSD1 oxidase and reductase activities in rat testis microsome with inhibitory constant of 1.2 and 2.9 mum, respectively. In intact Leydig cells, 7HT did not inhibit 11 beta-HSD1 reductase activity, but it stimulated its reductase activity. Thus, at 100 nm and higher concentrations, 7HT significantly switched 11 beta-HSD1 oxidoreductase activities toward reductase. The present data shows that 7HT, the product formed by CYP2A1 from testosterone, regulates the direction of 11 beta-HSD1 activity in rat Leydig cells.

Testosterone induction of prostaglandin-endoperoxide synthase 2 expression and prostaglandin F(2alpha) production in hamster Leydig cells

We have previously observed expression of prostaglandin-endoperoxide synthase 2 (PTGS2), the key enzyme in the biosynthesis of prostaglandins (PGs), in reproductively active Syrian hamster Leydig cells, and reported an inhibitory role of PGF(2alpha) on hamster testicular steroidogenesis. In this study, we further investigated PTGS2 expression in hamster Leydig cells during sexual development and photoperiodic gonadal regression. Since PTGS2 is mostly expressed in pubertal and reproductively active adult hamsters with high circulating levels of LH and androgens, we studied the role of these hormones in the regulation/maintenance of testicular PTGS2/PGF(2alpha). In active hamster Leydig cells, LH/hCG and testosterone induced PTGS2 and PGF(2alpha) production, and their actions were abolished by the antiandrogen bicalutamide (Bi). These results indicate that LH does not exert a direct effect on PG synthesis. Testosterone also stimulated phosphorylation of the mitogen-activated protein kinase isoforms 3/1 (MAPK3/1) within minutes and hours, but the testosterone metabolite dihydrotestosterone had no effect on PTGS2 and MAPK3/1. Because Bi and U0126, an inhibitor of the MAP kinase kinases 1 and 2 (MAP2K1/2), abolished testosterone actions on MAPK3/1 and PTGS2, our studies suggest that testosterone directly induces PTGS2/PGF(2alpha) in hamster Leydig cells via androgen receptors and a non-classical mechanism that involves MAPK3/1 activation. Since PGF(2alpha) inhibits testosterone production, it might imply the existence of a regulatory loop that is setting a brake on steroidogenesis. Thus, the androgen environment might be crucial for the regulation of testicular PG production at least during sexual development and photoperiodic variations in hamsters.

Failure of normal adult Leydig cell development in androgen-receptor-deficient mice

During testicular development, fetal and adult populations of Leydig cells arise sequentially. Previous studies have shown that androgen action is required for normal steroidogenic activity in the mouse testis. Therefore, to determine the role of androgens in regulating fetal and adult Leydig cell differentiation and function, Leydig development has been measured in mice lacking functional androgen receptors (AR-null). The Leydig cell number was normal on day 5 after birth in AR-null mice but failed to increase normally thereafter and was about 30% of the control level on day 20 and about 60% of control level in adult animals. Levels of 15 different mRNA species expressed specifically in Leydig cells were measured by real-time PCR in AR-null and control animals. Expression levels of all mRNA species were normal on day 5 when only fetal Leydig cells are present. In older animals, which contain predominantly adult Leydig cells, five of the mRNA species(3β-hydroxysteroid dehydrogenase (3βHSD) type 1, cytochrome P450scc,renin, StAR protein and luteinising hormone receptor) were expressed at normal or increased levels in AR-null mice. All other mRNA species measured showed significantly reduced expression in older animals, and three of these mRNA species (17β-hydroxysteroid dehydrogenase type III, prostaglandin D(PGD)-synthetase and 3βHSD type VI), which are only expressed in the adult population of Leydig cells, were barely detectable in the adult AR-null mouse. The results show that in the absence of androgen receptors, fetal Leydig cell function is normal, but there is a developmental failure of adult Leydig cell maturation, with cells only aquiring partial characteristics of the adult population.

Androgen metabolism in the different lobes of the prostate gland of intact, gonadectomized or hypophysectomized rats with or without androgen substitution

The effect of gonadectomy or hypophysectomy and the effect of substitution with testosterone, upon the reductive and oxidative metabolic transformations of testosterone, 4-androstene-3,17-dione, 17 beta-hydroxy-5 alpha-androstane-3-one, 5 alpha-androstane-3 alpha, 17 beta-diol and 5 alpha-androstane-3 beta, 17 beta-diol using NAD(H) and NADP(H) as added cofactors were examined in homogenates from the ventral (VP), lateral (LP) and dorsal prostate (DP), and coagulating gland (CG) of adult Wistar rats. The fall in serum testosterone induced by gonadectomy or hypophysectomy led to reduced activity of 5 alpha-reductase, NADP(H)-dependent 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR), NAD-dependent 3 alpha-HSOR, 3 beta-HSOR and 17 beta-HSOR, indicating that these enzymes are androgen dependent. The NADP dependent oxidation of 5 alpha-androstane-3 alpha, 17 beta-diol in LP increased upon hypophysectomy and gonadectomy. Testosterone substitution of gonadectomized or hypophysectomized rats generally maintained enzymatic activity at the level of the control group, except for the 5 alpha-reductase activity which fell in spite of this treatment. Hypophysectomy or gonadectomy had different effects on the activity of several androgen metabolizing enzymes; 5 alpha-reductase activity in DP and CG, NAD(H) dependent 3 alpha-HSOR in VP and NADPH dependent 3 beta-HSOR activity in LP, DP and CG. There were marked differences between the rat prostatic lobes, both concerning the activity of the androgen metabolizing enzymes and the responses to the different treatment modalities.

Immature rat Leydig cells are intrinsically less sensitive than adult Leydig cells to ethane dimethanesulfonate

Leydig cells from immature rat testes appear to be insensitive to doses of ethane-1,2-dimethanesulfonate (EDS) which eliminate Leydig cells from adult rat testes. We sought to determine whether this differential response to EDS is intrinsic to the Leydig cell or mediated by other intra- or extratesticular differences between adult and immature rats. To differentiate among these possibilities, Leydig cells were exposed to EDS (1) in vivo, (2) through in vitro testicular perfusion, or (3) in highly purified Leydig cell primary cultures. Four days after ip injections of 85 mg EDS/kg body wt Leydig cells were eliminated from testes of adult, but not immature rats. Total androgen production by testes perfused in vitro with 94 micrograms EDS/ml was dramatically reduced in adult, but not immature rats. Highly purified adult, but not immature, rat Leydig cells were far more sensitive to the effects of EDS on luteinizing hormone-stimulated androgen production (functional effects; apparent EC50 = 94 for adult and 407 micrograms/ml for immature rat Leydig cells) and on [35S]methionine incorporation (cytotoxic effects; apparent EC50 = 140 for adult and 1000 micrograms/ml for immature rat Leydig cells). Finally, the in vitro effects of EDS were both cell type and chemical specific. Since the differential response of adult and immature rat Leydig cells to EDS was manifest in vivo, during in vitro testicular perfusion, and in highly purified Leydig cell primary cultures, we conclude that immature rat Leydig cells are intrinsically less sensitive to the specific cytotoxic effects of EDS than adult rat Leydig cells.

Testicular autoregulation: possible role for 7-alpha-hydroxylated androgens

Pituitary FSH secretion appears to be supported by a factor distinct from the gonadotropin-releasing hormone (Gn-RH). The ratio of FSH to LH is positively correlated with testicular steroid 5 alpha-reductase activity and negatively correlated with testicular steroid 7 alpha-hydroxylase under various experimental conditions. Literature describing interactions among the above and other factors is reviewed here.

5 alpha-DHT metabolism in monolayer cultures of distinct pituitary cell populations

5 alpha-Dihydrotestosterone (DHT) metabolism into 5 alpha-androstane-3 alpha, 17 beta-diol (alpha-diol) and 5 alpha-androstane-3 beta, 17 beta-diol (beta-diol) was studied in monolayer cultures of distinct cell populations from prepubertal male rats pituitaries. Cells were characterized through immunocytochemistry with the various antihormone antisera. Centrifugal elutriation was used to prepare a gonadotrope-enriched population "G" and a gonadotrope-depleted population "L", containing most lactotropes and somatotropes. Using centrifugation on Percoll gradient, two sub-populations, P1 and P2, were prepared by further fractionation of the "L" population. Cells were incubated for 48 h with [3H]DHT (1 microM, sp. act. 0.9 Ci/mmol) and metabolites extracted from the whole cell and medium. DHT was metabolized to about the same extent (30-40%) in all cell fractions. Compared with unfractionated population, the conversion of DHT into alpha-diol increased significantly in the P1 fraction, consisting of lactotropes, somatotropes and highly depleted in gonadotropes. This increase was lower in the somatotrope-enriched P2 fraction in which the amount of lactotropes was similar to P1 but that of gonadotropes slightly higher. In contrast, the conversion of DHT into alpha-diol decreased significantly in the "G" population compared with total or "L" fractions, whereas androstanedione formation, low in every population, increased significantly. The increase in alpha-diol formation could be related either to the decrease of gonadotropes or to a role of non-immunoreactive cells. As the beta-diol formation was constant in all cell types, the beta-diol/alpha-diol amount increased significantly in gonadotropes. Then, beta-diol and DHT could be both active steroids in gonadotrope regulation inasmuch as specific binding sites were identified for these two steroids. It can be concluded that DHT action at the pituitary level is subject to complex control mechanisms involving a specific balance of its metabolites in each particular cell type.

Influence of a prolonged tamoxifen administration on steroidogenesis by incubated rat testes

Tamoxifen was administered i.m. for 9 days to adult male rats in a daily dose of 100 micrograms or 1 mg. The treatment resulted in a significant reduction of the plasma levels of testosterone and LH, without modification of the plasma levels of FSH and of the testes weight. Upon incubation, the testes from the tamoxifen-treated rats produced less testosterone and 7 alpha-hydroxytestosterone, but metabolized [4-14C]testosterone in the same way as the control animals. Small doses of hCG (0.5 i.u. for 9 days) were unable to modify the tamoxifen effect on the testicular function, while tamoxifen significantly inhibited the increase of the plasma levels of testosterone induced by the administration of moderate doses of hCG (1.5 i.u. or 2.5 i.u. for 9 days) to hypophysectomized rats. Tamoxifen treatment, however, did not modify significantly the reactivity of the testes towards high doses of hCG (10 i.u.), administered either 2 h before sacrifice or for 9 days. It is concluded that a prolonged administration of tamoxifen in the rat has, besides an indirect effect resulting from a decrease of the LH levels, a direct inhibitory influence on the testicular testosterone formation, which can be reversed by high doses of hCG.

Metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol in alveolar macrophages from rat lung--II. Effects of intratracheal instillation of 3.4 mumol K2Cr2O7

Activity of the steroid 5 alpha-reductase in pulmonary alveolar macrophages from adult male rats has been investigated in vitro. Intratracheal instillation of 3.4 mumol K2Cr2O7 lowered the enzyme activity within 6 h, and the reduction was significant on the subsequent 2, 4 and 7 days. The activity of this enzyme was significantly decreased only 6 and 24 h after instillation when measured in the 800 g supernatant fraction of whole lung. Instillation of 3.4 mumol K2Cr2O7 increased serum levels of corticosterone. Serum levels of triiodothyronine and thyroxine decreased except for a transient increase 3 h after the K2Cr2O7 instillation. Subcutaneous administration of 200 micrograms dexamethasone/100 g b.wt, 200 micrograms/100 g b.wt of testosterone, 17 beta-hydroxy-5 alpha-androstane-3-one (5 alpha-DHT), dehydroepiandrosterone or corticosterone had no effect on the 5 alpha-reductase activity of the pulmonary alveolar macrophages within 12 h. The combined treatment with dexamethasone s.c. and intratracheal instillation of 3.4 mumol K2Cr2O7 reduced the steroid 5 alpha-reductase activity in the pulmonary alveolar macrophages to about 25% of controls. Measurement of the steroid 5 alpha-reductase activity in pulmonary alveolar macrophages as an index of lung damage when exposed to toxic material is discussed.

Metabolism of androgens in the seminal vesicles and the different lobes of the prostate in young mature rats

Oxidation and reduction of 4-androstene-3,17-dione (androstenedione), 17 beta-hydroxy-4-androsten-3-one (testosterone), 17 beta-hydroxy-5 alpha-androstan-3-one (DHT), 5 alpha-androstan-3 alpha,17 beta-diol (3 alpha-A'diol) and 5 alpha-androstane-3 beta,17 beta-diol (3 beta-A'diol) were measured in homogenates from ventral (VP), dorsal (DP) and lateral prostate (LP), the coagulating gland (CG) and seminal vesicle (SV) of the intact sexually mature rat using NAD(H) or NADP(H) as cofactors. The specific activity of the various enzymes varied significantly between the different organs. 5 alpha-Reductase activity was highest in the DP and the CG, and undetectable in the LP. 17 beta-Hydroxysteroid oxidoreductase (17 beta-HSOR) activity was mainly confined to the LP. 3 alpha-Hydroxysteroid oxidoreductase (3 alpha-HSOR) activity was also highest in the LP. In the VP the highest 3 alpha-HSOR activity was recorded using NAD(H) as cofactor. In the other organs, similar or higher enzymatic activities were measured using NADP(H) as added cofactor. 3 beta-Hydroxysteroid oxidoreductase (3 beta-HSOR) activity was high in the LP and low or undetectable in the other tissues. Our results indicate that isoenzymes of 3 alpha-HSOR, 3 beta-HSOR and 17 beta-HSOR are present in the accessory sex organs of the rat.

A new dihydrotestosterone-forming index (DHTi)

A new index (DHTi) for the net formation of dihydrotestosterone (DHT) in a specific tissue is presented. This index is based on the main metabolic pathways forming DHT as well as on the main enzymatic activities removing DHT from the tissue. In the rat prostate, the DHTi is different in the various prostatic lobes. The index is highest in the ventral prostatic lobe, intermediate in the dorsal prostate and coagulating gland, and very low or undetectable in the seminal vesicles and the lateral prostatic lobe. With increasing age of the rats, the DHTi decreased. Testosterone treatment to old rats leads to an increased index.

Age dependent changes in androgen metabolism in the rat prostate

Oxidation and reduction of androstenedione, testosterone, dihydrotestosterone (DHT), 5 alpha-androstan-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol (3 alpha- and 3 beta-A'diol) were measured in homogenates from the ventral prostate (VP), dorsal prostate (DP), lateral prostate (LP), the coagulating gland (CG) and seminal vesicles (SV) in intact rats of different ages from young mature (3-6 months) to senescent rats (20-30 months). Some very old intact rats (30-32 months) were treated with testosterone in order to rule out the effect of this hormone on androgen metabolism. The enzymatic activities for young mature rats were significantly altered by increasing age, both with regard to differences between the various organs as well as differences in cofactor requirement. With increasing age, the specific activity of most enzymes gradually decreased. With testosterone as substrate, 5 alpha-reductase activity was significantly reduced in the old rats in all tissues studied and was undetectable in the oldest animals in the VP and the SV. On the other hand, 5 alpha-reductase could not be recorded in any tissue in any tissue in old rats when androstenedione was the substrate. 3 alpha-Hydroxysteroid oxidoreductase (3 alpha-HSOR) in the VP was the only enzyme which did not decrease in activity by increasing age. In the other lobes this enzyme activity decreased similar to 3 beta-hydroxysteroid oxidoreductase (3 beta-HSOR) and the 17 beta-hydroxysteroid oxidoreductase (17 beta-HSOR) activity. Administration of testosterone to old rats increased the specific activity of most of the enzymes studied.

Studies on the kinetics of the interaction of 7 alpha-hydroxytestosterone with the steroid 5 alpha-reductase

Microsomal preparations from adult male rat testicular interstitial cells were incubated with tritiated testosterone. Added 7 alpha-hydroxytestosterone, (7 alpha,17 beta-dihydroxy-4-androsten-3-one), at levels which appear to exist in the adult testis, inhibited production of labelled 5 alpha-reduced steroids in a graded fashion. This interaction is not competitive and occurs only at high substrate levels, such as those found in steroid-producing organs. Relationships to pubertal changes in steroid metabolism are discussed.

Metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol in alveolar macrophages from rat lung

5 alpha-Reduction of testosterone was observed in lung cells obtained by bronchoalveolar lavage (greater than 95% macrophages) from the rats. This activity was inhibited by progesterone and corticosterone. Production of 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol from testosterone was higher in rat pulmonary alveolar macrophages than by the 800 g supernatant fraction of whole lung homogenate from the same animals. Alveolar macrophages from rats treated with the 5 alpha-reductase inhibitor 17 beta-N,N-diethylcarbamoyl-4-aza-4-methyl-5 alpha-androstane-3-one (5 mg/100 g b.w., s.c.) showed decreased metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol 4 h after treatment. This metabolism was also decreased in alveolar macrophages from rats exposed to potassium dichromate by intratracheal instillation. When bovine alveolar macrophages were incubated with potassium dichromate, 5 alpha-reduction of testosterone decreased significantly. The function of steroid 5 alpha-reduction in alveolar macrophages is currently not known.

Testosterone metabolism by incubated rat testes after chronic LHRH treatment

Adult male rats were injected 4 or 8 days with LHRH agonist. After sacrifice the testes were incubated in vitro with or without [4-14C]testosterone. After LHRH-administration the endogenously produced amounts of testosterone and of 7 alpha-hydroxytestosterone, the main testosterone metabolite normally found on incubation of adult rat testes, were drastically reduced when compared with controls. hCG, injected to rats 2 h before sacrifice, increased steroid production. In the LHRH-treated rats, however, the amounts of testosterone and of 7 alpha-hydroxytestosterone produced were much less while an important formation of 5 alpha-androstanediol was observed. The testes of LHRH treated rats metabolized [4-14C]testosterone to a large extent to 5 alpha-reduced and unextractable metabolites while the formation of 7 alpha-hydroxylated metabolites was much reduced. It is concluded that prolonged LHRH treatment provokes not only a depression of the testosterone production but has also an influence on the testicular metabolism pattern of testosterone resulting in a proportionally increased production of 5 alpha-reduced steroids and unextractable metabolites while the formation of 7 alpha-hydroxylated steroids is inhibited.

7-Alpha-hydroxytestosterone in seminiferous tubules of rat testis

Production of 4-androstene-7 alpha,17 beta-diol-3-one (7 alpha-hydroxytestosterone) from testosterone was measured in seminiferous tubule and interstitial fractions of rat testis. In adults, specific activity of the 7 alpha-hydroxylase was about 10 times higher in interstitial cells than in seminiferous tubules, but tubule production was a significant portion of the total. Seminiferous tubule 7 alpha-hydroxylase was not detectable in weanlings. Also, we confirmed that 7 alpha-hydroxytestosterone inhibits the activity of the 5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase active on testosterone and suggest a role in maturational changes.

In vitro metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol by the rat intestine

The metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol by the 800 g supernatant fraction by different parts of the gastrointestinal tract from male rats was investigated. This metabolism tended to be higher in immature than in mature animals. Administration of dexamethasone or long-acting ACTH to immature and mature rats increased testosterone metabolism to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol by ileum tissue. No such effect could be observed following administration of progesterone, estradiol, prolactin, LH or FSH in mature animals. Development of the gastrointestinal tract from the immature to the mature stage was associated with augmented metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol in the ileum.

Effects in vitro of medroxyprogesterone acetate on steroid metabolizing enzymes in the rat: selective inhibition of 3 alpha-hydroxysteroid oxidoreductase activity

The effects of 6 alpha-methyl-17 alpha-acetoxy-4-pregnene 3,20-dione (MPA) on the activity of different steroid metabolizing enzymes in vitro were investigated in several organs in the rat. MPA seems to be a potent inhibitor of 3 alpha-reduction of 17 beta-hydroxy-5 alpha-androstan-3-one (Dht) in homogenates of the testis, ovary, epididymis, prostate, kidney and the adrenal glands. In testicular homogenates MPA acts like a competitive inhibitor of the 3 alpha-reduction of Dht, with Ki of 0.42 [microM]. MPA seems to be a selective inhibitor of 3 alpha-hydroxysteroid oxidoreductase in numerous organs. Steroid metabolizing enzymes like 5 alpha-reductase, 7 alpha-hydroxylase, 3 beta-hydroxysteroid oxidoreductase and 17 beta-hydroxysteroid oxidoreductase were not inhibited by MPA under the conditions of incubation employed in these studies.

Stimulation in vivo of testicular 7 alpha-hydroxylase activity in immature rats by LH and hCG

Testicular C19-steroid 7 alpha-hydroxylase activity rises during puberty in the rat. Hormonal mechanisms responsible for this rise are unknown. The present study is to the best of our knowledge the first to report successful stimulation of testicular 7 alpha-hydroxylase in immature rats. Administration of crude and purified hCG every day for 3 or more days to immature rats in doses of 3 I.U. lead to significant stimulation of testicular 7 alpha-hydroxylase activity. Purified preparations of subunits of hCG did not stimulate 7 alpha-hydroxylase activity. Stimulation of testicular 7 alpha-hydroxylase was, however, recorded when purified subunits of hCG were allowed to recombine and then administered to the animals. Several preparations of LH failed to cause stimulation of 7 alpha-hydroxylase when administered to immature rats. Treatment of immature rats with mixtures of LH and FSH, LH and prolactin or LH together with FSH and prolactin was also ineffective in this respect. Large doses of highly purified ovine-LH, rat LH and human LH were, however, able to stimulate testicular 7 alpha-hydroxylase activity in immature rats. Preparations comprising hybrids of ovine-LH and hCG (oLH alpha + hCG beta, hCG alpha + oLH beta) stimulated testicular 7 alpha-hydroxylase activity in immature rats. Administration of the same amounts of a hybrid preparation of human and ovine-LH (oLH alpha + hLH beta) to immature rats was ineffective in this respect. Administration of testosterone or estradiol to immature rats lead to suppression of testicular 7 alpha-hydroxylase activity. Combined treatment of such rats with hCG and testosterone or with estradiol and hCG augmented testicular 7 alpha-hydroxylase activity to the same degree as that of animals treated with hCG only.

C-19-steroid 7 alpha-hydroxylation by rat testes. Isolation and identification of: 7 alpha, 17 beta-dihydroxy-5 alpha-androstan-3-one, 5 alpha-androstan-3 alpha, 7 alpha, 17 beta-triol and 5 alpha-androstane-3 beta, 7 alpha, 17 beta-triol

From incubations of testosterone with rat testicular homogenates in the presence of a NADPH-generating system, the following 7 alpha-hydroxylated metabolites could be isolated and identified: 7 alpha, 17 beta-dihydroxy-4-androsten-3-one (7 alpha-hydroxy-testosterone), 7 alpha-17 beta-dihydroxy-5 alpha-androstan-3-one (7 alpha-hydroxy-Dht), 5 alpha-androstan-3 alpha, 7 alpha, 17 beta-triol (7 alpha-hydroxy-3 alpha-A'DIOL) and 5 alpha-androstane-3 beta, 7 alpha, 17 beta-triol (7 alpha-hydroxy-3 beta-A'DIOL). To our knowledge this is the first demonstration of the formation of 5 alpha-reduced-7 alpha-hydroxylated metabolites of testosterone in the male gonad. These 5 alpha-reduced-7 alpha-hydroxylated metabolites could also be isolated after incubations of 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-A'DIOL) with testicular homogenates in the presence of A NADPH-generating system. Measured as the sum of 7 alpha-hydroxy-testosterone, 7 alpha-hydroxy-Dht. 7 alpha-hydroxy-3 alpha-A'DIOL and 7 alpha-hydroxy-3 beta-A'DIOL formed using testosterone as substrate, total 7 alpha-hydroxylase activity was six times higher in testes of mature rats than in testes from animals 23 days old. With 3 alpha-A'DIOL as substrate total 7 alpha-hydroxylase in the mature testis was about three times greater than in the sexually immature testis.

Effect of dihydrotestosterone on rat liver alcohol dehydrogenase activity

Castration was previously demonstrated to result in an increase in liver alcohol dehydrogenase and in rates of ethanol elimination in male rats. In this study, the effect of dihydrotestosterone, which is a more potent androgen than testosterone in the rat, was determined on liver alcohol dehydrogenase and ethanol elimination in the castrated rat. Dihydrotestosterone was found to be a substrate of liver alcohol dehydrogenase in the reductive direction and a competitive inhibitor of ethanol oxidation by the enzyme. Also, the administration of a single dose of dihydrotestosterone inhibited liver alcohol dehydrogenase 4 hr after the injection, but this effect was not persistent at later intervals following injection. This transient in vivo inhibition of liver alcohol dehydrogenase was associated with a delay in ethanol elimination. The microsomal ethanol-oxidizing enzyme system was found to play no role in the changes in ethanol elimination observed after castration and dihydrotestosterone administration since its activity remained unchanged. These studies provide further evidence of an effect of androgenic steroids on liver alcohol dehydrogenase activity and ethanol metabolism.

Synthesis and androgen effects of 7 alpha,17 beta-dihydroxy-5 alpha-androstan-3-one, 5 alpha-androstan-3 alpha,7 alpha,17 beta-triol and 5 alpha-androstane-3 beta,7 alpha,17 beta-triol

The steroids 7 alpha,17 beta-dihydroxy-5 alpha-androstan-3-one (7 alpha-hydroxy-Dht), 5 alpha-androstan-3 alpha,7 alpha,17 beta-triol (7 alpha-hydroxy-3 alpha-A'DIOL) and 5 alpha-androstane-3 beta,7 alpha,17 beta-triol (7 alpha-hydroxy-3 beta-A'DIOL) have been synthetized from 7 alpha,17 beta-dihydroxy-4-androsten-3-one (7 alpha-hydroxy-testosterone). The effect of administering 7 alpha-hydroxy-Dht, 7 alpha-hydroxy-3 alpha-A'DIOL or 7 alpha-hydroxy-3 beta-A'DIOL on serum levels of LH, FSH and on ventral prostate and seminal vesicle weight were investigated in gonadectomized adult male rats. Each steroid was administered for seven days in a dose of 300 micrograms per day. No suppression of serum LH or FSH levels was recorded following injections of these 7 alpha-hydroxylated steroids to castrated rats, compared to castrated control rats receiving vehicle only. Administration of 7 alpha-hydroxy-Dht or 7 alpha-hydroxy-3 alpha-A'DIOL to castrated mature rats could maintain ventral prostate and seminal vesicle weights above that of castrated control rats. Administration of 7 alpha-hydroxy-3 beta-A'DIOL to castrated mature rats resulted in ventral prostate weights slightly above castrate control levels, while seminal vesicle weight in such rats were in the same range as castrated control rats. Intraperitoneal administration of testosterone or of 5 alpha-androstane-3 beta,17 beta-diol (3 beta-A'DIOL) to castrated rats maintained activity of the androgen dependent isoenzyme of acid phosphatase in the ventral prostate; 7 alpha-hydroxy-testosterone or 7 alpha-hydroxy-3 beta-A'DIOL showed, however, no effect on this enzymic activity.

Role of testosterone levels and of hypophysis in the HCG-induced modifications of the 7 alpha-hydroxylation and 5 alpha-reduction processes in incubated rat testes

The role of a direct or a hypophysis-mediated influence of increased testosterone levels in the effects of a long-term high-dose HCG administration (10 IU/day) upon the 7 alpha-hydroxylation and 5 alpha-reduction activities of incubated testes of mature rats was investigated. Administration of high doses of HCG to hypophysectomized rats resulted in the same metabolic changes as in normal rats, namely, a large decrease in the 7 alpha-hydroxylation and an increase in the 5 alpha-reduction processes. Administration of testosterone-propionate (0.2 mg and 20 mg/day) for several days to hypophysectomized rats and to normal rats receiving and substitutive dose of 1 IU HCG/day, did not modify the testicular metabolization pattern. These findings indicate that the decrease in testicular 7 alpha-hydroxylation activity induced by long-term administration of high doses of HCG is probably not mediated by the hypophysis nor by the extracellular testosterone levels.

Modulation of steroidogenic activities in testis Leydig cells

Recent developments in the regulation of testicular Leydig-cell function support the following conclusions. (1) Enzymic activities involved in steroid production in the testis are mainly localized in Leydig cells. The aromatase enzyme complex for oestrogen production appears to be localized in Leydig cells as well as in Sertoli cells. (2) LH- (or hCG-) induced alterations of Leydig cells depend on dose and duration of exposure of the cell to the hormone. Locally produced oestradiol is probably involved in the inhibition of steroidogenesis. (3) The stimulatory action of LH on Leydig cells involves different proteins in concert with the activation of the cleavage activity of mitochondrial cholesterol side-chain. However, most of the functional properties of these proteins are yet unknown. (4) Different populations of Leydig cells are present in the testis. These different cell populations can be characterized by quantitatively and qualitatively different responses to hormones.

Metabolism of 5 alpha-androstane-3 beta,17 beta-diol to 17 beta-hydroxy-5 alpha-androstan-3-one and 5 alpha-androstan-3 alpha,17 beta-diol in the rat

Significant metabolism of 5 alpha-androstane-3 beta,17 beta-diol to 17 beta-hydroxy-5 alpha-androstan-3-one was recorded in several tissues and organs from rats and humans. This bioconversion was further investigated in rat testis homogenates. 5 alpha-Androstane-3 beta,17 beta-diol was readily metabolized to 17 beta-hydroxy-5 alpha-androstan-3-one with NAD and/or NADP added as cofactors. When a NADPH generating system was included in the incubation, 5 alpha-androstane-3 beta,17 beta-diol was metabolized to 5 alpha-androstan-3 alpha,17 beta-diol. Only small amounts of 17 beta-hydroxy-5 alpha-androstan-3-one accumulated under the latter condition.