Steroidogenesis by cultured granulosa cells aspirated from human follicles using pregnenolone and androgens as precursors

Human granulosa cells from Graafian follicles aspirated 3-4 h before the expected time of ovulation were incubated with various steroid substrates, including pregnenolone, androstenedione, testosterone and dehydroepiandrosterone (DHA). Steroid production after 3 and 10 h of incubation was determined by radioimmunoassay. Progesterone and 17alpha-hydroxyprogesterone were the major products of granulosa cells in control short-term cultures with endogenous substrates. The addition of pregnenolone increased the synthesis of progesterone and 17alpha-hydroxyprogesterone compared with the controls, although the response varied considerably between paired short-term cultures. Little or no oestradiol-17beta was produced from endogenous precursors or short-term cultures to which pregnenolone had been added; one follicle, however, produced similar amounts of oestradiol-17beta in the control cultures and after incubation with pregnenolone. When granulosa cells were cultured with various amounts of androstenedione, DHA or testosterone, large amounts of oestradiol-17beta were produced, especially in short-term cultures in which larger amounts of substrate were added. Progesterone production continued and progesterone was synthesized more rapidly or in greater amounts in some short-term test cultures than in the controls. The results indicate that human granulosa cells are one source of oestradiol-17beta during the preovulatory phase. The data support the two-cell theory for oestradiol synthesis, for granulosa cells do not appear to undertake steroid conversion via the 5-unsaturated pathway, but aromatize androgens known to be produced by thecal cells. It is also suggested that either androgens or oestradiol-17beta stimulate progesterone production by granulosa cells, at least in vitro.     

Mevinolin, an inhibitor of cholesterol biosynthesis, drastically depresses Ca2+ channel activity and uncouples excitation from contraction in cardiac cells in culture.

Mevinolin (MK803), a potent inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) (Ki, 30 X 10(-9) M), depressed de novo synthesis of cholesterol in 11-day chicken embryonic cardiac cells cultured in lipoprotein-deficient serum (LPDS). Cardiac cells exposed to different concentrations of mevinolin for 1-3 days presented different electrophysiological and mechanical properties: The resting membrane potential, the rate of increase, and the shape of the action potential and contractile properties were changed at concentrations as low as 0.1 microM mevinolin. At a concentration of 1 microM mevinolin, the cardiac cells became quiescent and electrical stimulation induced action potentials of short duration without contraction. Isoproterenol and Bay K8644 were unable to restore excitability and contraction. Although the number of receptors for the tritiated Ca2+ channel blocker nitrendipine was the same in control and in mevinolin-treated cells, voltage-clamp data on isolated cardiac cells and 45Ca2+ flux experiments on monolayers showed that most of the slow Ca2+ channel activity was lost in mevinolin-treated cells. These results suggest that the disappearance of Ca2+ channel activity is most probably at the origin of the loss of cardiac contractility.     

Site at which ovarian nerve extracts inhibit thecal androgen production

We have recently reported that extracts of the superior ovarian nerve (SON) of rats inhibit porcine theca cell androstenedione production. Theca cells obtained from prepubertal gilts were cultured under serum-free conditions for 48 h. The inhibitory effect of SON extracts occurred within 6 h of treatment, was irreversible and independent of the dose of luteinizing hormone (LH) employed. The SON extracts' actions were exerted at a site(s) distal to the generation of adenosine 3',5'-monophosphate (cyclic AMP), since they did not affect extracellular cyclic AMP accumulation, while causing a significant inhibition of androstenedione production. The SON extract decreased 17 alpha-hydroxyprogesterone, androstenedione, testosterone, estradiol and estrone production while increasing progesterone and pregnenolone production, suggesting that the SON extract causes an inhibition of the 17 alpha-hydroxylase:C17-20 lyase complex. These results indicate that a factor(s) in the SON may play an important role in the regulation of follicular development, since thecal androgens are substrates for granulosa cell estrogen biosynthesis and are also involved in follicular atresia.     

Effects of tumor necrosis factor-alpha in vitro on steroidogenesis of healthy and atretic follicles of the rat: theca as a target

Tumor necrosis factor-alpha (TNF), a pleiotropic cytokine localized within the ovary, alters follicular steroidogenesis. Preovulatory follicles dissected from ovaries of normal cyclic adult rats on the morning of proestrus exhibit steroidogenic and histological signs of atresia after 24 h of culture under the conditions of 5% CO2 and air. Follicles cultured for 24 h in 5% CO2 and 95% O2 appeared histologically and steroidogenically healthy. Under both culture conditions, human recombinant TNF (5 ng/ml) significantly increased the production of pregnenolone, progesterone, 20 alpha-dihydroprogesterone, and 17 alpha-hydroxyprogesterone by the follicles. Follicles cultured in 5% CO2 and air exhibited no change in androstenedione or estradiol production compared to control follicles incubated without TNF. In contrast, follicles cultured in 5% CO2 and 95% O2 responded to TNF with increased androstenedione and estradiol production. Separation of the thecal and granulosa compartments indicated that the increased progestin production observed in the whole follicle in response to TNF originated from the theca. TNF significantly inhibited basal and FSH-stimulated progesterone production from the granulosa of preovulatory follicles. Exogenous substrate added to whole follicles cultured in the presence or absence of TNF indicated that TNF enhanced the conversion of 25-hydroxycholesterol to pregnenolone. These studies reveal that TNF enhanced steroidogenesis in both healthy and atretic follicles and that this action of TNF is on the theca, where TNF increases the conversion of cholesterol to pregnenolone. The data imply that TNF has differential effects on thecal and granulosa steroidogenesis.     

Regulation of steroid production in cultured porcine thecal cells by transforming growth factor-beta.

Evidence that transforming growth factor-beta (TGF beta) is produced by porcine thecal cells and acts upon porcine granulosa cells suggests that this peptide may be a local regulator of follicular function in this species. The objective of the present study was to investigate the effects of TGF beta on steroidogenesis in thecal cells from 4-6 mm follicles of prepubertal gilts. In this culture system, cells undergo functional luteinization such that production of androstenedione, the major steroid product in 24 h incubations, declines, and in the presence of luteinizing hormone (LH) (250 ng/ml) and insulin (1 micrograms/ml), progesterone production increases over a 3-day culture period. TGF beta (0.1-10 ng/ml) had no effect on production of androstenedione from endogenous precursors in the presence or absence of LH, although there was a slight inhibition of androstenedione production in the presence of exogenous progesterone (up to 23%). As the cells luteinized in culture, the increase in progesterone production in response to LH increased (day 1, 4.4-fold; day 3, 13-fold). TGF beta at concentrations as low as 0.1 ng/ml caused marked (up to 90%) inhibition of LH-stimulated progesterone production in day 3 cultures. In the presence of TGF beta (10 ng/ml), the response to LH was completely abolished, and the response to dibutyryl cAMP was considerably attenuated (25% of controls). Since the primary site of action of TGF beta appeared to be distal to cAMP formation, the effect of TGF beta on conversion of exogenous 22-hydroxy-cholesterol and pregnenolone to progesterone was determined in day 3 cultures. 22-Hydroxycholesterol and pregnenolone restored progesterone production to at least 80% and 89% of controls, respectively. While the primary inhibitory action of TGF beta appears to be exerted distal to cAMP formation, neither cholesterol sidechain cleavage nor the 3 beta-hydroxysteroid dehydrogenase: delta 5-delta 4 isomerase reactions are primary targets of this factor. Together with evidence of thecal production of TGF beta, the results of this study indicate that this peptide may be an autocrine regulator of thecal steroidogenesis.     

Biosynthetic pathways of testosterone and estradiol-17 beta in slices of the embryonic ovary and testis of the chicken (Gallus domesticus)

To elucidate synthetic pathways of testosterone and estradiol-17 beta in embryonic gonads of the chicken, metabolism of various 14C-labeled steroids in slices of the left ovaries and paired testes of 15- and 9-day-old chicken embryos was examined. (1) Fifteen-day-old chicken embryos: From pregnenolone, more 17 alpha-hydroxypregnenolone was produced than progesterone in the ovary, while more progesterone was produced than 17 alpha-hydroxypregnenolone in the testis. From 17 alpha-hydroxypregnenolone, however, only dehydroepiandrosterone was detected as a product in both gonads. Dehydroepiandrosterone was converted mainly into androstenedione and its 5 beta-reduced derivatives by both gonads. Progesterone was converted into 5 beta-pregnane-3,20-dione more than into 17 alpha-hydroxyprogesterone by both gonads. Both gonads metabolized 17 alpha-hydroxyprogesterone, androstenedione, and testosterone predominantly into their corresponding 5 beta-reduced steroids, while production of androstenedione from 17 alpha-hydroxyprogesterone and of testosterone from androstenedione was limited. Estradiol-17 beta was produced from androstenedione and testosterone only by the ovary. (2) Nine-day-old chicken embryos: From pregnenolone, production of progesterone and 17 alpha-hydroxypregnenolone was similar in the ovary. On the other hand, in the testis, more progesterone was produced than 17 alpha-hydroxypregnenolone from pregnenolone. For delta 4-3-oxo steroids, strong activity of 5 beta-reductase was demonstrated in both gonads. From these results, both delta 4- and delta 5-pathways are involved in the formation of testosterone and then finally of estradiol-17 beta by the embryonic gonads of the chicken, and relative preference for the pathway seems to depend on sexes and embryonic ages. In addition, it is suggested that steroidogenesis in these embryonic gonads is characterized by marked activity of 5 beta-reductase, irrespective of sexes or ages.     

Mechanisms subserving calcium's modulation of luteinizing hormone action in isolated swine granulosa cells

We studied the mechanism(s) by which calcium ions modulate progesterone biosynthesis by isolated swine granulosa cells incubated in chemically defined medium in vitro. In selectively calcium-deficient incubations, the capacity of 8-bromo-cAMP to stimulate pregnenolone synthesis from endogenous sterol substrate was significantly impeded. This effect of calcium ions was specific, because calcium ions did not influence basal pregnenolone production or alter progesterone production in response to exogenously supplied cholesterol substrate. Moreover, calcium ions did not modify other biosynthetic processes in granulosa cells, such as de novo synthesis of cholesterol from [14C]acetate or the aromatization of testosterone to 17 beta-estradiol. The possible role of calmodulin in mediating calcium's actions in pig granulosa cells was tested by measuring the calmodulin content of these cells and assessing the functional responses to classical calmodulin antagonists. By immunoassay, swine granulosa cells contained high concentrations of calmodulin, viz. 4.21-4.88 micrograms calmodulin/mg protein. Moreover, calmodulin antagonists inhibited LH-stimulated progesterone production with the following rank order of potencies [estimated by half-maximally inhibitory concentrations (ID50)]: penfluridol (1 microM), trifluoroperazine (9 microM), chlorpromazine (95 microM), and trifluoperazine sulfoxide (greater than 300 microM). In addition, the nonphenothiazine calmodulin antagonist W7 inhibited stimulated progesterone production with an ID50 of 16.7 microM. W5 was less active. None of these antagonists significantly suppressed LH-stimulated cAMP generation at the low concentrations capable of inhibiting progesterone production. The effects of calcium ions seemed to depend upon the availability of intracellular pools of calcium, because TMB-8, an inhibitor of intracellular calcium mobilization, effectively suppressed LH-stimulated progesterone production (ID50, 18 microM). However, even 100 microM TMB-8 failed to alter basal progesterone production or suppress LH-stimulated cAMP generation in these cells. In summary, the present studies indicate that calcium ions significantly modulate LH's stimulation of pregnenolone biosynthesis from endogenous cholesterol substrate in swine ovarian cells. Calcium does not influence basal pregnenolone production, estrogen synthesis from androgen substrate, de novo biosynthesis of cholesterol from [14C]acetate, or progesterone production from exogenously supplied sterol substrate.(ABSTRACT TRUNCATED AT 400 WORDS)     

Pathways of testosterone synthesis in decapsulated testes of mice.

In order to study the temporal relations in the biogenesis of testosterone, decapsulated testes of adult mice were incubated with carbon-14-labelled sodium acetate and attempts were made to isolate the most likely intermediates. Considerable quantities of radiochemically homogeneous squalene, lanosterol, cholesterol, testosterone and androstenedione, but no pregnenolone, progesterone, 17-hydroxypregnenoline, 17-hydroxyprogesterone, dehydroepiandrosterone, pregnenolone sulphate or dehydroepiandrosterone sulphate were isolated. The same pattern of incorporation was found when gradually increasing amounts of non-labelled pregnenolone, progesterone, 17-hydroxypregenenolone, 17-hydroxyprogesterone, dehydroepiandrosterone, dehydroepiandrosterone sulphate or testosterone were added to the system as "trapping agents" or when Leydig cell preparations rather than decapsulated testes were used. The presence of 10 mIU of HCG greatly enhanced the de novo formation of testosterone, androstenedione and 5alpha-dihydrotestosterone but did not change the pattern of acetate incorporation. Radioimmunoassays of the incubation medium with or without added HCG, and carried out at different periods of time indicated the presence of gradually increasing amounts of testosterone and androstenedione together with some 5alpha-dihydrotestosterone, whereas only trace amounts of pregnenolone, progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone and dehydroepiandrosterone were present. An analysis of the incubated testes revealed that the addition of HCG significantly enhanced the content of testosterone, androstenedione and 5alpha-dihydrotestosterone. Little or no increase was observed as far as pregnenolone, progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone or dehydroepiandrosterone were concerned. It is concluded that decapsulated testes of mice synthesize de novo testosterone from sodium acetate under conditions in which the formation of pregnenolone, progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone, pregnenolone sulphate and 17-hydroxypregnenolone sulphate cannot be demonstrated.     

Partial 17, 20-desmolase and 17 alpha-hydroxylase deficiencies in a 16-year-old boy

Thirteen plasma steroids as well as ACTH, LH and FSH were measured by specific RIAs under basal and dynamic conditions in a 16-year-old boy (normal external genitalia, 46, XY karyotype) who presented slowness and unachievement of pubertal development. On the delta 4-pathway: basal levels of testosterone and dihydrotestosterone were low- with a normal ratio-, delta 4-androstenedione and 11 beta-hydroxyandrostenedione were in the low normal range. Meanwhile, 17 alpha-hydroxyprogesterone and progesterone levels were markedly elevated. On the delta 5-pathway: dehydroepiandrosterone was extremely low while 17 alpha-hydroxypregnenolone and pregnenolone were almost normal; dehydroepiandrosterone sulfate was subnormal while pregnenolone sulfate was normal. Cortisol, aldosterone were normal while ACTH was moderately increased. Basal and responsive levels of LH and FSH were markedly increased. ACTH stimulation induced a subnormal rise of cortisol and 11 beta-hydroxyandrostenedione, a low or absent rise of dehydroepiandrosterone, 17 alpha-hydroxypregnenolone, androstenedione and 17 alpha-hydroxyprogesterone contrasting with a marked rise of pregnenolone and progesterone. After hCG stimulation, responses were low for testosterone, extremely high for 17 alpha-hydroxyprogesterone with a normalisation of the 17 alpha-hydroxyprogesterone/progesterone ratio. Fluoxymesterone dramatically reduced the pathologically high basal levels of progesterone and 17 alpha hydroxyprogesterone. Dexamethasone induced only a minute decrease in the delta 4-progestagens, a marked decrease in pregnenolone, with a more than 80% reduction of 17 alpha- hydroxypregnenolone, dehydroepiandrosterone, dehydroepiandrosterone sulfate and androstenedione. These data suggest a defect involving the cytochrome P450 common to both 17 alpha-hydroxylase and 17, 20-desmolase activities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Site of androgen inhibition of follicle-stimulating hormone-stimulated progesterone production in porcine granulosa cells

In granulosa cells derived from medium-sized porcine follicles, certain androgens have been shown to inhibit FSH-stimulated progesterone synthesis. To determine the site at which this inhibition takes place, the effects of androgens on FSH- and (Bu)2cAMP-stimulated pregnenolone and progesterone syntheses were examined. Granulosa cells were isolated from 4- to 6-mm follicles and cultured for 24 h in modified Eagle's Minimum Essential Medium, alone or with FSH (1 microgram/ml) or (Bu)2cAMP (0.5-4 mM) in the presence or absence of androstenedione or testosterone. (Bu)2cAMP stimulated progesterone production in a dose-dependent manner. Testosterone (5 microM) had a slight, but nonsignificant, inhibitory effect on basal progesterone production, but significantly inhibited the synthesis of progesterone in the presence of (Bu)2cAMP, suggesting that testosterone inhibits progesterone synthesis at a step distal to cAMP formation. In the absence of FSH, granulosa cells produced substantial quantities of pregnenolone. FSH caused a 3-fold stimulation of pregnenolone synthesis. The addition of androstenedione or testosterone (5 microM) markedly increased pregnenolone accumulation in FSH-treated cultures. To determine at what step androgens affected FSH-stimulated pregnenolone production, granulosa cells were cultured with (Bu)2cAMP and/or testosterone for 24 h. (Bu)2cAMP stimulated pregnenolone synthesis in a dose-dependent manner. Testosterone (5 microM) significantly increased pregnenolone synthesis in response to (Bu)2cAMP, suggesting that androgens acted at a step distal to cAMP formation. Since these concentrations of androgens markedly inhibited FSH-stimulated progesterone production by these preparations, these results suggest that androgens may affect the conversion of pregnenolone to progesterone.     

The effects of o,p'-DDD on human adrenal steroid synthesis

In the present study, the effects of o,p'-DDD on plasma levels of pregnenolone, 17 alpha-hydroxypregnenolone, progesterone, 17 alpha-hydroxyprogesterone, 11-deoxycorticosterone, deoxycortisol, corticosterone, cortisol, androstenedione and testosterone were studied in 6 patients with adrenal carcinoma (3 with Cushing's syndrome, 2 with adrenogenital syndrome, one without clinical manifestation) and 6 with Cushing's disease. Plasma levels of these steroids were decreased in all of the patients with adrenal carcinoma. The decrement of progesterone and 17 alpha-hydroxyprogesterone was greater than that of pregnenolone and 17 alpha-hydroxypregnenolone. These results indicate that o,p'-DDD inhibits both cholesterol cleavage enzyme and 3 beta-hydroxysteroid dehydrogenase coupled with delta 5 to 4 isomerase system. Plasma levels of pregnenolone and 17 alpha-hydroxypregnenolone showed a twofold increase on the 7th day after consecutive administrations of o,p'-DDD in patients with Cushing's disease. Plasma levels of cortisol were decreased to normal one month after continuous o,p'-DDD treatment. Urinary 17-OHCS and 17-KS have been decreased out of proportion to the decrease in plasma cortisol in the first week of o,p'-DDD treatment. Such a disparity suggests that o,p'-DDD might affect the extra-adrenal metabolism of cortisol. However, no evidence was found for the inhibition of hepatic C17-20lyase and glucuronyl transferase. Regression of pulmonary metastases was observed in one case with Cushing's syndrome due to adrenal carcinoma, suggesting that o,p'-DDD causes necrosis of the metastatic adrenal carcinoma. A remission of the disease was obtained in one patient with Cushing's disease after 6 months of continuous o,p'-DDD treatment. The usefulness of o,p'-DDD for the treatment of adrenal carcinoma with metastases and Cushing's disease was confirmed.     

Steroid metabolism in the testes of the breeding and nonbreeding three-spined stickleback, Gasterosteus aculeatus

Steroid metabolism in the testes of sticklebacks was studied in vitro by tissue incubations with [3H]pregnenolone or [3H]androstenedione as precursors. In males in full reproductive condition (nesting), [3H]pregnenolone was mainly converted via progesterone and 17 alpha-hydroxyprogesterone into androstenedione, 11 beta-hydroxyandrostenedione, and 11-ketoandrostenedione. The latter was the largest product formed. The main products from the [3H]androstenedione incubation, 11 beta-hydroxyandrostenedione and 11-ketoandrostenedione, confirm these findings. The rate of androgen synthesis, especially of 11-ketoandrostenedione, was much lower after the end of the breeding season.     

Regulation of androstenedione production by adenosine 3',5'-monophosphate and phorbol myristate acetate in ovarian thecal cells of the domestic hen

Although factors that regulate cAMP and steroid production in granulosa cells of hen preovulatory follicles have been well studied, much less is known of the mechanisms that control steroidogenesis in the adjacent thecal layer. These studies were conducted to examine the involvement and interaction of cAMP and protein kinase-C in modulating androstenedione output from isolated ovarian thecal cells collected from the second largest preovulatory follicle. Treatment of thecal cells with ovine LH (0.01-100 ng/tube) caused a dose-dependent increase in androstenedione secretion. Although coincubation of cells with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.1 mM) potentiated the effects of LH on steroid production, cAMP levels increased only in response to the higher doses of LH (10-100 ng/tube). Small but significant increases in cAMP accumulation and androstenedione production were observed in response to vasoactive intestinal peptide (0.1 and 1.0 microM), but not to 100 ng/tube chicken FSH, in the presence of 0.1 mM 3-isobutyl-1-methylxanthine. Treatment of thecal cells with cholera toxin (0.001-100 ng/tube) or forskolin (0.001-10 microM) resulted in a dose-dependent increase in cellular cAMP levels and androstenedione secretion. Thecal cell androstenedione production was also stimulated by the cAMP analog 8-bromo-cAMP (0.1-1.0 mM). Incubation of thecal cells with phorbol 12-myristate 13-acetate (PMA; 0.32-162 nM) or 1-oleoyl-2-acetylglycerol (OAG; 2.5-126 microM) increased basal steroidogenesis (progesterone and androstenedione production) in the absence of a rise in cAMP levels. By contrast, the stimulatory effects of 1 ng/tube LH on androstenedione, but not progesterone, production were attenuated by the presence of PMA (3.2-162 nM) or OAG (25-126 microM). Only a high concentration of OAG (126 microM) suppressed cAMP accumulation stimulated by LH (50 ng/tube). Phorbol ester treatment (32-162 nM PMA) also inhibited androstenedione production in thecal cells stimulated by the presence of 8-bromo-cAMP (1 mM), indicating a post-cAMP effect of protein kinase-C activity on steroidogenesis. In contrast to the effects of PMA, phorbol 13-monoacetate (162 nM), a nontumor-promoting analog of PMA which does not activate protein kinase-C, did not alter basal steroidogenesis, nor did it affect androstenedione secretion stimulated by LH or 8-bromo-cAMP. Data from the present studies indicate that the adenylyl cyclase-cAMP pathway can mediate the induction of thecal cell steroidogenesis by extracellular signals (i.e. LH and vasoactive intestinal peptide), whereas activated protein kinase-C can both stimulate and inhibit androstenedione production, depending upon the hormonal environment.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cyclosporine inhibits testosterone biosynthesis in the rat testis

To determine whether the immunosuppressive agent cyclosporine (CsA) has an effect on testicular androgen function in the male rat, four groups of adult animals were treated daily for 28 days with either orange juice or three doses of CsA (7.5, 15, or 30 mg/kg X day). Twenty-four hours after the last dose of CsA, the animals were killed and the following parameters were measured: testis, seminal vesicle, and ventral prostate weights; serum levels of CsA, creatinine, testosterone (T), and LH; and intratesticular levels of pregnenolone, progesterone, 17 alpha-hydroxyprogesterone, androstenedione, and T. There were no differences between the control (orange juice) and the three CsA-treated groups with respect to serum creatinines and testis, seminal vesicle, and ventral prostate weights. Serum T decreased significantly in the 15 and 30 mg/kg CsA-treated groups. The intratesticular T level decreased significantly only in the 15 and 30 mg/kg CsA-treated groups. In the 15 and 30 mg/kg CsA-treated groups, the intratesticular pregnenolone, progesterone, and 17 alpha-hydroxyprogesterone levels all showed a significant decline compared to controls. There was no significant change in the androstenedione levels in any of the CsA-treated groups. To determine whether the decrease in T production by the testis exposed to CsA is via inhibition of the hypothalamic-pituitary axis, serum LH was measured in all four groups. Serum LH decreased significantly only in the 15 and 30 mg/kg CsA-treated groups. These data suggest that oral CsA administration in doses greater than 15 mg/kg X day results in diminished intratesticular T production that appears to be mediated via inhibition of pituitary LH function.     

A quantitative study of steroid bioconversions in the testis of the African catfish, Clarias gariepinus (Burchell), under natural spawning and natural and cultivated non-spawning conditions

Quantitative aspects of bioconversions in the testes of the African catfish (Clarias gariepinus) were studied in vitro by incubation of tissue with [3H]pregnenolone or [3H]androstenedione. During the breeding period, spawning and non-spawning animals were collected from their natural habitat, the Hula nature reserve, in northern Israel. In the same period, non-spawning animals were collected from a fish pond in the same region. It was shown that spawning was accompanied by significant changes in steroid bioconversions, i.e. a reduction in androgen synthesis, especially of 11 beta-hydroxyandrostenedione and 11 beta-hydroxytestosterone and an increase in the production of C21-steroids, especially progesterone, 17 alpha-hydroxyprogesterone and a pregnenolone ester. These changes resulted from a decreased contribution of the cytochrome P-450 enzymes 17 alpha-hydroxylase, C17-20-lyase and 11 beta-hydroxylase. A rise in plasma gonadotrophin concentration was observed only in spawning catfish. In the absence of such an increase in plasma gonadotrophin, steroid synthesis in the testes of non-spawning feral and pond catfish was primarily directed towards the production of 11-oxygenated androgens and 5 beta-pregnane-3 alpha,17 alpha,20 alpha-triol. It is suggested that spawning is induced by gonadotrophin and the ensuing change in steroidogenesis. It is possible that husbandry conditions inhibit the necessary increase in gonadotrophin release.     

Opposite effect of human chorionic gonadotropin on placental and ovarian synthesis of androstenedione

In the present studies, we have investigated the role of human chorionic gonadotropin on the biosynthesis of androgens by placentas and corpora lutea of the pregnant rat. We first sought to compare the effect of hCG on placental and ovarian secretion of androstenedione in vivo. For this purpose either 1.5 IU hCG or vehicle was administered to pregnant rats twice on days 12 and 13 and once on the morning of day 14. Blood was obtained from either the ovarian or the uterine vein. After hCG administration, levels of androstenedione secreted in the ovarian vein increased dramatically, whereas those in the uterine vein declined significantly. To establish that changes in androgen levels in the uterine and ovarian veins are due to changes in biosynthetic activity and also to compare the action of hCG on placentas and corpora lutea, tissues were dissected out from rats treated with 0, 1.5, or 9 IU hCG twice daily and incubated in vitro. hCG administration increased the capacity of luteal cells to synthesize androstenedione de novo by approximately 100% and concomitantly decreased placental secretion of androstenedione by approximately 75%. Addition of high density lipoprotein to the medium enhanced both basal and hCG-stimulated androstenedione production by luteal tissues but had no effect on either basal or hCG-inhibited androstenedione biosynthesis by the placenta. To determine which step in the placental biosynthesis of androstenedione is inhibited by increased levels of LH, we determined the effect of hCG administration, on cholesterol biosynthesis and storage, synthesis of progesterone substrate, and the activities of 17 alpha-hydroxylase/17,20-lyase. hCG did not affect the activities of the rate limiting cholesterogenic enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase, placental content of cholesterol and cholesteryl ester, or the placental production of progesterone. However, hCG did cause a substantial decrease in the activity of 17 alpha-hydroxylase/17,20-lyase enzyme(s); responsible for the conversion of progesterone to androgen. In summary, results of the present investigation demonstrate that increases in LH activity in the circulation act on two different steroidogenic glands to either enhance or reduce androgen biosynthesis. hCG stimulates luteal secretion of androstenedione and simultaneously inhibits placental production of this steroid.(ABSTRACT TRUNCATED AT 400 WORDS)     

Regulation of cholesterol side-chain cleavage and 17 alpha-hydroxylase/lyase activities in proliferating human theca interna cells in long term monolayer culture

In this report we describe the development and characterization of a long term culture system to study regulation of the expression of 17 alpha-hydroxylase, cholesterol side-chain cleavage, and 3 beta-hydroxysteroid dehydrogenase in human theca interna cells. Conditions have been established for the dispersal, growth, freezing, and storage of functional human theca interna cells isolated from preovulatory follicles of women undergoing laparoscopy for gamete intrafallopian tube transfer and in vitro fertilization procedures. Theca interna cells grown under these conditions have a doubling rate of 28-32 h and are morphologically distinct from human granulosa cells grown under the same conditions. Theca interna cells were grown, passed for successive passages, and transferred into serum-free medium containing forskolin, hCG, LH, or cAMP analogs. There was a time- and dose-dependent increase in 17 alpha-hydroxylase activity and progesterone synthesis from endogenous precursors. Added pregnenolone was converted to 17 alpha-hydroxypregnenolone, which was further converted primarily to dehydroepiandrosterone and, to a much lesser extent, androstenedione. Progesterone was converted to 17 alpha-hydroxyprogesterone and 16 alpha-hydroxyprogesterone. In studies using 17 alpha-hydroxyprogesterone as substrate, no metabolism to androstenedione or any other product was detectable. Similarly, 4-pregnen-20 alpha-ol-one (20 alpha-dihydroprogesterone) was not metabolized to any detectable products. Northern analysis performed on total RNA obtained from forskolin-stimulated theca interna cultures verified that the increase in 17 alpha-hydroxylase activity was associated with a corresponding increase in levels of mRNA specific for 17 alpha-hydroxylase cytochrome P-450. Message levels for cholesterol side-chain cleavage P-450 were similarly increased in cells treated with forskolin. No detectable mRNA encoding aromatase cytochrome P-450 was discerned. This procedure for the preparation and study of proliferating human theca internal cells provides an opportunity to study regulation of the expression of steroidogenic enzymes and other cellular processes unique to human ovarian cells.     

Effects of luteinizing hormone withdrawal on Leydig cell smooth endoplasmic reticulum and steroidogenic reactions which convert pregnenolone to testosterone

Depletion of endogenous LH with sc implants of testosterone-17 beta-estradiol (T-E) caused a reduction in the Leydig cell smooth endoplasmic reticulum (SER) over a 10-day treatment period. Decreases also occurred in some, but not all, of the testicular steroidogenic reactions responsible for the conversion of pregnenolone (PREG) to testosterone. The conversions of progesterone (PROG) to 17 alpha-hydroxyprogesterone, 17 alpha-hydroxyprogesterone to androstenedione, and androstenedione to testosterone were significantly correlated (P less than 0.05) with the loss of Leydig cell SER. In contrast, the testicular conversion of PREG to PROG in rats deprived of endogenous LH for up to 10 days was identical to that in intact controls. Similar results were obtained when rats were hypophysectomized for 10 days. These results indicate that the Leydig cell enzyme activities responsible for converting PREG to PROG are distributed in the Leydig cell SER fraction which remains in Leydig cell cytoplasm 10 days after LH withdrawal, and thus, the bulk of these enzyme activities are sequested in a SER compartment that is resistant to LH withdrawal.     

Bone morphogenetic protein inhibits ovarian androgen production

Bone morphogenetic proteins (BMPs), members of the transforming growth factor beta superfamily, were recently shown to be expressed and to regulate steroidogenesis in rat ovarian tissue. The purpose of this study was to investigate the effect of BMP-4 on androgen production in a human ovarian theca-like tumor (HOTT) cell culture model. We have previously demonstrated the usefulness of these cells as a model for human thecal cells. HOTT cells respond to protein kinase A agonists by increased production of androstenedione and with an induction of steroid-metabolizing enzymes. In this investigation, HOTT cells were treated with forskolin or dibutyryl cyclic AMP (dbcAMP) in the presence or absence of various concentrations of BMP-4. The accumulation of androstenedione, progesterone, and 17alpha-hydroxyprogesterone (17OHP) in the incubation medium was measured by RIA. The expression of 17alpha-hydroxylase (CYP17), 3beta-hydroxysteroid dehydrogenase (3betaHSD), cholesterol side-chain cleavage (CYP11A1), and steroidogenic acute regulatory (StAR) protein was determined by protein immunoblotting analysis using specific rabbit polyclonal antibodies. We also examined the expression of BMP receptor subtypes in our HOTT cells using RT-PCR. In cells treated with medium alone, steroid accumulation and steroid enzyme expression was unchanged. In cells treated with BMP alone there was a modest decrease in androstenedione secretion. In the presence of forskolin, HOTT cell production of androstenedione, 17OHP, and progesterone increased by approximately 4.5-, 35-, and 3-fold, respectively. In contrast, BMP-4 decreased forskolin-stimulated HOTT cell secretion of androstenedione and 17OHP by 50% but increased progesterone production 3-fold above forskolin treatment alone. Forskolin treatment led to an increase in CYP17, CYP11A1, 3betaHSD, and StAR protein expression. BMP-4 markedly inhibited forskolin stimulation of CYP17 expression but had little effect on 3betaHSD, CYP11A1, or StAR protein levels. Similar results were observed with the cAMP analog dbcAMP. In addition, BMP-4 inhibited basal and forskolin stimulation of CYP17 messenger RNA expression as determined by RNase protection assay. Other members of the transforming growth factor beta superfamily, including activin and inhibin, had minimal effect on androstenedione production in the absence of forskolin. In the presence of forskolin, activin inhibited androstenedione production by 80%. Activin also inhibited forskolin induction of CYP17 protein expression as determined by Western analysis. We identified the presence of messenger RNA for three BMP receptors (BMP-IA, BMP-IB, and BMP-II) in the HOTT cells model. In conclusion, BMP-4 inhibits HOTT cell expression of CYP17, leading to an alteration of steroidogenic pathway resulting in reduced androstenedione accumulation and increased progesterone production. These effects of BMP-4 seem similar to those caused by activin, another member of the transforming growth factor-beta superfamily of proteins.     

The skin of the male African catfish, Clarias gariepinus: a source of steroid glucuronides

Steroid metabolism in the skin of mature male African catfish, Clarias gariepinus, reared in the laboratory, was studied in vitro by tissue incubations with [3H]pregnenolone, [3H]dehydroepiandrosterone, [3H]17 alpha-hydroxyprogesterone, [3H]androstenedione, [14C]11 beta-hydroxyandrostenedione, and [3H]testosterone as precursors. While pregnenolone was not converted to any other steroid, dehydroepiandrosterone was transformed mainly to 5-androstene-3 beta, 17 beta-diol. The products of 17 alpha-hydroxyprogesterone incubations were 5 beta-pregnane-3 alpha,17 alpha-diol-20-one, 5 beta-pregnane-3 alpha,17 alpha, 20 beta-triol, and 5 beta-pregnan-17 alpha-o1-3,20-dione. The major steroids of androstenedione incubations were etiocholanolone, testosterone, and androsterone. Testosterone was converted mainly to etiocholanolone and androstenedione, and only small quantities of 11 beta-hydroxytestosterone, 11-ketotestosterone, and 11-ketoandrostenedione were the metabolites found in 11 beta-hydroxyandrostenedione incubation. These results demonstrated the presence of the enzymes 5 alpha- and 5 beta-reductases and 3 alpha-, 11 beta-, 17 beta-, and 20 beta-hydroxysteroid dehydrogenases in the skin. From enzymehistochemical results it appeared that the steroid conversions take place in the epithelial cells. Moreover, the presence of UDP-glucose dehydrogenase, an enzyme involved in the synthesis of glucuronic acid, in these cells indicates the possibility of steroid glucuronide formation. Indeed significant amounts of water-soluble steroid conjugates, particularly 5 beta-dihydrotestosterone- and testosterone-glucuronide, were found in the incubations with androstenedione and testosterone, indicating the presence of the UDP-glucuronosyl transferase in the catfish skin. In the light of these results, a role of the skin of African catfish in the production of semiochemicals having pheromonal properties is discussed.