One-pot efficient synthesis of 13(R),14(R)-epoxy-17β-methyl-20(S)-hydroxyl-18-nor-pregna-4-en-3-one via a tandem epoxidation-rearrangement-epoxidation reaction sequence

One-pot synthesis of an 18-norsteroid compound, 13(R),14(R)-epoxy-17β-methyl-20(S)-hydroxyl-18-nor-pregna-4-en-3-one has been achieved with peracetic acid/acetic acid under a mild condition, via a proved tandem epoxidation-rearrangement-epoxidation sequence. Its structure was designated on the basis of NMR and X-ray crystallography data.

Opposing actions of the progesterone metabolites, 5alpha-dihydroprogesterone (5alphaP) and 3alpha-dihydroprogesterone (3alphaHP) on mitosis, apoptosis, and expression of Bcl-2, Bax and p21 in human breast cell lines

Previous studies have shown that breast tissues and breast cell lines convert progesterone (P) to 5alpha-dihydroprogesterone (5alphaP) and 3alpha-dihydroprogesterone (3alphaHP) and that 3alphaHP suppresses, whereas 5alphaP promotes, cell proliferation and detachment. The objectives of the current studies were to determine if the 5alphaP- and 3alphaHP-induced changes in cell numbers are due to altered rates of mitosis and/or apoptosis, and if 3alphaHP and 5alphaP act on tumorigenic and non-tumorigenic cells, regardless of estrogen (E) and P receptor status. The studies were conducted on tumorigenic (MCF-7, MDA-MB-231, T47D) and non-tumorigenic (MCF-10A) human breast cell lines, employing several methods to assess the effects of the hormones on cell proliferation, mitosis, apoptosis and expression of Bcl-2, Bax and p21. In all four cell lines, 5alphaP increased, whereas 3alphaHP decreased cell numbers, [(3)H]thymidine uptake and mitotic index. Apoptosis was stimulated by 3alphaHP and suppressed by 5alphaP. 5alphaP resulted in increases in Bcl-2/Bax ratio, indicating decreased apoptosis; 3alphaHP resulted in decreases in Bcl-2/Bax ratio, indicating increased apoptosis. The effects of either 3alphaHP or 5alphaP on cell numbers, [(3)H]thymidine uptake, mitosis, apoptosis, and Bcl-2/Bax ratio, were abrogated when cells were treated simultaneously with both hormones. The expression of p21 was increased by 3alphaHP, and was unaffected by 5alphaP. The results provide the first evidence that 5alphaP stimulates mitosis and suppresses apoptosis, whereas 3alphaHP inhibits mitosis and stimulates apoptosis. The opposing effects of 5alphaP and 3alphaHP were observed in all four breast cell lines examined and the data suggest that all breast cancers (estrogen-responsive and unresponsive) might be suppressed by blocking 5alphaP formation and/or increasing 3alphaHP. The findings further support the hypothesis that progesterone metabolites are key regulatory hormones and that changes in their relative concentrations in the breast microenvironment determine whether breast tissues remain normal or become cancerous.

GABAergic neurosteroids mediate the effects of ethanol on long-term potentiation in rat hippocampal slices

We previously found that ethanol has complex effects on hippocampal synaptic plasticity, inhibiting long-term potentiation (LTP) and long-term depression by different mechanisms. The block of long-term depression appears to be mediated by effects on N-methyl-d-aspartate receptors, whereas the block of LTP involves augmented inhibition via gamma-aminobutyric acid-A receptors (GABA(A)Rs). To pursue factors contributing to effects on LTP, we examined the ability of various concentrations of ethanol to block LTP in the CA1 region of rat hippocampal slices. Complete LTP block required 60 mm ethanol. LTP block was enhanced at lower ethanol concentrations in the presence of (3alpha5alpha)-3-hydroxypregnan-20-one, a GABA(A)R-potentiating neurosteroid, suggesting that neurosteroids may be important contributors to the effects of ethanol on LTP. Consistent with this, we found that block of LTP by 60 mm ethanol was overcome by coadministration of a cyclodextrin that binds and removes lipophilic neurosteroids. More specifically, treatment of slices with finasteride, an agent that inhibits the synthesis of 5alpha-reduced neurosteroids, or with an agent that inhibits the effects of 5alpha-reduced neurosteroids on GABA(A)Rs overcame the effects of 60 mm ethanol on LTP. Taken together, these results indicate that acute production of GABA(A)R-enhancing neurosteroids plays a key role in mediating the effects of ethanol on LTP.

Membrane 5alpha-pregnane-3,20-dione (5alphaP) receptors in MCF-7 and MCF-10A breast cancer cells are up-regulated by estradiol and 5alphaP and down-regulated by the progesterone metabolites, 3alpha-dihydroprogesterone and 20alpha-dihydroprogesterone, with associated changes in cell proliferation and detachment

Previous studies have shown that the progesterone metabolite, 5alpha-pregnane-3,20-dione (5alphaP), exhibits mitogenic and metastatic activity in breast cell lines and that specific, high affinity receptors for 5alphaP are located in the plasma membrane fractions of tumorigenic (ER/PR-positive) MCF-7 cells. The aim of this study was to determine the effects of the mitogenic (estradiol; 5alphaP) and anti-mitogenic (3alpha-hydroxy-4-pregnen-20-one, 3alphaHP; 20alpha-hydroxy-4-pregnen-3-one, 20alphaHP) endogenous steroid hormones on 5alphaP receptor (5alphaP-R) numbers and on cell proliferation and adhesion of MCF-7 and MCF-10A cells. Exposure of MCF-7 cells for 24h to estradiol or 5alphaP resulted in significant (p < 0.05-0.001) dose-dependent increases in 5alphaP-R levels. Conversely, treatment with 3alphaHP or 20alphaHP resulted in significant (p < 0.05-0.01) dose-dependent decreases in 5alphaP-R levels. Treatment with one mitogenic and one anti-mitogenic hormone resulted in inhibition of the mitogen-induced increases, whereas treatment with two mitogenic or two anti-mitogenic hormones resulted in additive effects on 5alphaP-R numbers. Treatments with cycloheximide and actinomycin D indicate that changes in 5alphaP-R levels depend upon transcription and translation. The non-tumorigenic breast cell line, MCF-10A, was also shown to posses specific, high affinity plasma membrane receptors for 5alphaP that were up-regulated by estradiol and 5alphaP and down-regulated by 3alphaHP. Estradiol binding was demonstrated in MCF-10A cell membrane fractions and may explain the estradiol action in these cells that lack intracellular ER. In both MCF-7 and MCF-10A cells, the increases in 5alphaP-R due to estradiol or 5alphaP, and decreases due to 3alphaHP or 20alphaHP correlate with respective increases and decreases in cell proliferation as well as detachment. These results show distribution of 5alphaP-R in several cell types and they provide further evidence of the significance of progesterone metabolites and their novel membrane-associated receptors in breast cancer stimulation and control. The findings that 3alphaHP and 20alphaHP down-regulate 5alphaP-R and suppress mitogenic and metastatic activity suggest that these endogenous anti-mitogenic progesterone metabolites deserve considerations in designing new breast cancer therapeutic agents.

Pathogenesis of diabetic neuropathy--do hyperglycemia and aldose reductase inhibitors affect neuroactive steroid formation in the rat sciatic nerves?

The activation of the polyol pathway through aldose reductase (AR) might be involved in diabetic neuropathy. A considerable structural similarity exists between AR and 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) (both belonging to aldo-keto reductase superfamily); 3alpha-HSD forms 5alpha-reduced-3alpha-hydroxylated steroids, possibly possessing neurotrophic functions. Aim of these experiments was to test "in vitro" in rat sciatic nerves, whether glucose concentrations in the diabetic range might affect the capacity of 3alpha-HSD to transform dihydroprogesterone (DHP) into tetrahydroprogesterone (THP), a steroid proved to possess neurotrophic effects. The capability of AR inhibitors, drugs used to avoid diabetic complications, to decrease THP formation was also assessed. 3alpha-HSD activity was evaluated by the conversion of labelled DHP into THP (in a single case dihydrotestosterone was used as substrate, and the corresponding 3alpha-hydroxylated metabolite was evaluated). Freshly prepared rat sciatic nerve homogenates were used as source of the enzyme. Whole brain, liver and prostate served as "control" tissues. The results show that glucose added up to a concentration of 400 mg/dL (well above the euglycemic upper level) does not affect the 3alpha-HSD activity in the sciatic nerve and in the other tissues considered. Similarly, when the enzyme was challenged by two AR inhibitors, tolrestat and sorbinil, added in a concentration about 10 times higher than their IC50 for AR, no significant changes were observed. Analogous results were achieved when DHT was used in presence of glucose (400 mg/dL) and sorbinil. We conclude that hyperglycemia or the administration of the AR inhibitors do not affect 3alpha-HSD activity in peripheral nerves and therefore do not reduce the formation of steroid metabolites possibly endowed with neurotrophic action.

Biosynthesis of the neurosteroid 3 alpha-hydroxy-4-pregnen-20-one (3 alpha hp), a specific inhibitor of FSH release

The gonadal steroid 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP) is a neuroactive steroid with anxiolytic and analgesic actions. In addition, 3 alpha HP has been shown to inhibit GnRH activity on gonadotropes and selectively suppress FSH release from pituitary cells, without an effect on LH. The enzyme 3 alpha-hydroxysteroid dehydrogenase (3 alpha HSD) has been presumed to be the enzyme responsible for the conversion of progesterone to 3 alpha HP, but this has never been confirmed in vitro or in vivo. We have now determined the mechanism of 3 alpha HP synthesis in vivo using specific enzyme inhibitors and in vitro using recombinant proteins. Incubation of [(3)H]progesterone with purified recombinant rat and human 3 alpha HSD isoforms showed that both the rat 3 alpha HSD and the human type 2(brain) 3 alpha HSD converted progesterone to 3 alpha HP. Age-dependent 3 alpha HP production was demonstrated in pituitary and cortex. Incubation of both tissues with indomethacin, a known 3 alpha HSD inhibitor, decreased the conversion of progesterone to 3 alpha HP by at least 70%, indicating that 3 alpha HSD was responsible for this conversion. As human type 2 3 alpha HSD is expressed in a region-specific fashion in the brain, 3 alpha HP may only be made in specific regions of the brain. Furthermore, the data suggest that the pituitary has the capacity for 3 alpha HP production, which may provide an additional mechanism for regulation of GnRH action.

Plasma membrane receptors for the cancer-regulating progesterone metabolites, 5alpha-pregnane-3,20-dione and 3alpha-hydroxy-4-pregnen-20-one in MCF-7 breast cancer cells

Recent observations indicate that the progesterone metabolite, 5alpha-pregnane-3,20-dione (5alphaP), which is produced at higher levels in tumorous breast tissue, promotes cell proliferation and detachment, whereas 3alpha-hydroxy-4-pregnen-20-one (3alphaHP), which is produced at higher levels in nontumorous breast tissue, suppresses proliferation and detachment of MCF-7 breast cancer cells. The objective of the current study was to determine the presence and characteristics of binding sites for these endogenous putative cancer-regulating steroid hormones. Radiolabeled 5alphaP and 3alphaHP were used in radioligand binding assays on MCF-7 cell (membrane, cytosolic, and nuclear) fractions. Binding of [(3)H]5alphaP and [(3)H]3alphaHP was observed only in the plasma membrane fraction, whereas estradiol binding sites were confirmed in the cytosolic and nuclear fractions. The respective membrane binding sites exhibited specificity for the 5alphaP and 3alphaHP ligands with no appreciable displacement at 200- to 500-fold excess by other steroids. The association rate constants were calculated as 0. 107/min and 0.0089/min and the dissociation rate constants were 0. 049 9 and 0.011 for 5alphaP and 3alphaHP, respectively. Saturation analyses indicated single classes of molecules with dissociation constants of 4.5 and 4.87 nM and receptor densities of 486 and 629 fmol/mg protein, respectively, for 5alphaP and 3alphaHP. Exposure of MCF-7 cells to estradiol for 1, 24, 48, and 72 h resulted in 2.3, 4. 2-, 2.99-, and 1.7-fold increases, respectively, in 5alphaP receptor density. 3alphaHP resulted in partial suppression of the estradiol-mediated increase in 5alphaP receptor density. This is the first report of receptors for the progesterone metabolites, 5alphaP and 3alphaHP, of their occurrence in breast cancer cell membranes, and of the induction of 5alphaP receptors by estradiol. The results provide further support for the potential importance of progesterone metabolites in breast cancer.

Brief exposure of mice to 60 Hz magnetic fields reduces the analgesic effects of the neuroactive steroid, 3alpha-hydroxy-4-pregnen-20-one

Relatively weak, extremely low frequency (ELF), magnetic fields have been shown to exert a variety of biological effects, although the modes of action remain to be established. Neuroactive steroids and neurosteroids have been shown to produce a diverse range of rapid centrally mediated behavioral and physiological effects that are reported to be sensitive to magnetic fields. Here we show that brief exposure of male mice to an ELF magnetic field (30 min, 60 Hz, 141 microT peak) significantly reduces the analgesic effects arising from intracerebroventricular (i.c.v.) administration of the centrally produced allylic neuroactive steroid, 3alpha-hydroxy-4-pregnen-20-one (3alphaHP) and that the dihydropyridine (DHP) calcium channel antagonists, diltiazem and nifedipine, block the inhibitory effects of the 60 Hz ELF on 3alphaHP-induced analgesia. These results indicate that exposure to 60 Hz ELF affects the analgesic effects of neuroactive steroids such as 3alphaHP through alterations in calcium channel function. These findings raise the possibility that ELF magnetic fields may, in part, exert their actions through effects on diverse neuroactive steroid modulated processes.

Synthesis, metabolism and levels of the neuroactive steroid, 3alpha-hydroxy-4-pregnen-20-one (3alphaHP), in rat pituitaries

The neuroactive steroid, 3a-hydroxy-4-pregnen-20-one (3alphaHP), is a metabolite of progesterone and a precursor of 3alpha-hydroxy-5alpha-pregnan-20-one (5alphaP3alpha; allopregnanolone). In addition to analgesic and anxiolytic effects by interaction with the GABA(A) receptor complex, 3alphaHP regulates pituitary FSH secretion by rapid non-genomic interaction with the Ca2+-driven cell signaling mechanisms. Since gonadectomy and adrenalectomy do not result in elimination of 3alphaHP, and since there is the possibility of paracrine and/or autocrine regulation of FSH release, the capacity of pituitary cells to regulate levels (by synthesis, metabolism, and storage) of 3alphaHP was examined. Anterior pituitaries from random cycling female rats were incubated, either as fragments or as cultured cells, for 1, 4 or 8 h with 3H- or 14C-labeled progesterone. The steroid metabolites were identified by thin-layer chromatography, autoradiography, high pressure liquid chromatography (HPLC), derivatization and GC/MS. Pituitary cells actively converted progesterone to 3alphaHP along with 5alphaP3alpha, 5alpha-pregnane-3,20-dione, 20alpha-hydroxy-5alpha-pregnan-3-one, 3beta-hydroxy-5alpha-pregnan-20-one, 5alpha-pregnane-3alpha(beta), 20alpha-diols, 20alpha-hydroxy-4-pregnen-3-one, and 4-pregnene-3alpha(beta), 20alpha-diols. The results indicate the presence of the following steroidogenic enzymes in anterior pituitary cells: 3alpha-hydroxysteroid oxidoreductase (3alpha-HSO), 20alpha-HSO, 3beta-HSO, and 5alpha-reductase. The activities of 5alpha-reductase and 3alpha-HSO were approximately equal and greatly exceeded those of the other enzymes. After 8 h of incubation with 100 ng progesterone per pituitary, about 20% of the progesterone was metabolized and 3.18 ng of 3alphaHP had been formed. The accumulation of 3alphaHP increased approximately linearly with the time of incubation. Metabolism studies using [1,2,6,7-(3)H]3alphaHP showed that pituitary cells convert about 29% and 8% of the 3alphaHP to progesterone and 5alphaP3alpha, respectively, in 2 h. Specific radioimmunoassays determined 11.6 and 7.5 ng of 3alphaHP per pituitary, respectively, in 25- and 40-day-old non-cycling female rats; these concentrations of 3alphaHP were about 2-3-fold greater than those of progesterone in the same pituitaries. In older (80-100 days old) cycling rats, the levels of 3alphaHP were about 9.4 and 18.6 ng/pituitary at 13.00 h and 22.00 h, respectively, on the day of proestrus, while the concomitant circulating levels were 13.7 and 5.4 ng/ml. The results indicate a marked capacity of rat pituitary cells to synthesize the neuroactive and FSH regulating steroid, 3alphaHP, from progesterone, and in turn to metabolize 3alphaHP to the neurosteroid, allopregnanolone, and to progesterone. The studies suggest cyclic biosynthetic and metabolic pathways for 3alphaHP and other steroids in the pituitary. They also indicate that the regulation of FSH secretion by 3alphaHP may be (in part, or in whole) via paracrine or autocrine mechanisms.

Acute, nongenomic actions of the neuroactive gonadal steroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), on FSH release in perifused rat anterior pituitary cells

We have previously shown that the gonadal and neurosteroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), can selectively suppress gonadotrophin-releasing hormone (GnRH) induced follicle-stimulating hormone (FSH) release from static cultures of anterior pituitary cells during a 4-h incubation period. The actions appeared to be at the level of the gonadotroph membrane and the cell signaling pathway involving Ca2+ and protein kinase C (PKC). In order to investigate further if the effects of 3 alpha HP on FSH release are generated by nongenomic mechanisms, we monitored the short-term effects of 3 alpha HP using dispersed anterior pituitary cells in a low dead-volume perifusion system with short (< or = 5 min) exposures to the steroid. Pulses of GnRH (10(-8) or 10(-7) M) lasting 2-5 min resulted in marked peaks of FSH release, and the variation in FSH amounts released from the cells in a particular column were minimal if the interval between successive GnRH pulses was at least 3-4 h. A 5-min pulse of 3 alpha HP (10(-9) M) administered simultaneously with the GnRH pulse suppressed GnRH-induced FSH release. On the other hand, similar treatment with the stereoisomer 3 beta-hydroxy-4-pregnen-20-one (3 beta HP), had no effect, but progesterone and estradiol pulses augmented the GnRH-induced FSH release. Pretreatment of cells with a 5-min pulse of 3 alpha HP, at 120, 60, or 30 min prior to a GnRH pulse suppressed the GnRH-induced FSH release. The suppression of GnRH-induced FSH release by 3 alpha HP was only partial if the start of the 3 alpha HP pulse occurred 0.5 or 1.0 min after the start of the GnRH pulse, and no suppression occurred if the start of the 3 alpha HP pulse was delayed by 2-5 min. The FSH release elicited by 5-min pulses of the Ca2+ ionophore A23187, the Ca2+ agonist BAY K8644, the PKC activator phorbol 12-myristate 13-acetate (PMA), or phospholipase C (PLC) was suppressed by simultaneous pulses of 3 alpha HP. The suppression of FSH release by 3 alpha HP appeared to be stereospecific, since no suppression was observed with 5 alpha-pregnane-3,20-dione (5 alpha P) or 3 alpha-hydroxy-5 alpha-pregnan-20-one (5 alpha P3 alpha). In separate experiments, cells were treated with pulses of BSA conjugates of 3 alpha HP, 3 beta HP, or progesterone; the 3 alpha HP-BSA, but not the 3 beta HP-BSA or the progesterone-BSA, suppressed the GnRH-induced release of FSH. The results of this study provide the first evidence that 3 alpha HP exerts immediate (nongenomic) and direct effects on GnRH-induced FSH release by interacting at the level of the pituitary gonadotroph membrane and the phosphoinositol cell signaling cascade involving Ca2+.

Nongenomic actions of steroids on gonadotropin release

The release of gonadotropins is effected by GnRH and regulated by steroids. The classical mechanism of steroid hormone action, which implies the binding of hormone receptor complexes to regulatory elements of nuclear genes, is derived largely from the well-studied and familiar steroids such as progesterone, testosterone, and estradiol. Their effects on gonadotropin release generally have been examined following hours or days of exposure and therefore cannot account for the rapid effects of steroids on gonadotropin release. Moreover, tissues such as gonad, pituitary, and hypothalamus can produce a variety of hormonally active steroids in addition to these well-studied, traditional ones. The recently discovered allylic steroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), is readily interconverted from/to progesterone and is found at appreciable levels in serum, gonads, pituitary, hypothalamus, and other tissues. 3 alpha HP has provided the "missing link" in the progesterone biosynthetic/ metabolic pathways, allowing cyclical 4-pregnene and 5 alpha-pregnane pathways to be described for steroidogenic tissues. Among the functions ascribed to 3 alpha HP is the ability to selectively and rapidly (within seconds or minutes) suppress GnRH-provoked FSH release. In vitro studies using pituitary gonadotropes in culture and in perifusion paradigms suggest that suppression of FSH release by 3 alpha HP occurs as a result of nongenomic mechanisms of action. These mechanisms are discussed and include interaction at the level of receptors in the gonadotrope membrane and the cell-signaling pathway involving protein kinase C, phospholipase C, or IP3-induced Ca2+ mobilization and Ca2+ channels. This may be the first evidence of a gonadal steroid regulating gonadotropin release by nongenomic mechanisms of action. In order to understand the critical role of steroids in the rapid regulation of secretory (and bence, circulating) levels of gonadotropins, other gonadal steroids will need to be examined for their nongenomic action on gonadotropes.

Progesterone and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OHP) in the pregnant baboon: selective placental secretion of 20 alpha-OHP into the fetal compartment

The serum concentrations of progesterone and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OHP) were measured by RIA in blood draining the maternal and fetal sides of the placenta on Day 100 and Day 170 of gestation (term = Day 184) in the baboon to determine the qualitative and quantitative patterns of progestins within the maternal-placental-fetal compartment and to ascertain whether production of placental progestins is increased with advancing gestation. The mean (+/- SEM) concentration of progesterone in maternal serum was similar at mid- (10 +/- 2 ng/ml) and late (11 +/- 3 ng/ml) gestation and not different than that of 20 alpha-OHP (6 +/- 1 ng/ml). In the uterine vein, progesterone levels were greater (p < 0.05) at Day 100 (82 +/- 13 ng/ml) than at Day 170 (30 +/- 7 ng/ml) and exceeded (p < 0.05) those of 20 alpha-OHP at both mid- (8 +/- 2 ng/ml) and late (4 +/- 1 ng/ml) gestation. Progesterone concentrations in the umbilical vein (128 +/- 24 ng/ml) and artery (79 +/- 12 ng/ml) at midgestation exceeded respective values at term (20 +/- 1 and 14 +/- 1 ng/ml). In contrast, 20 alpha-OHP concentrations in the umbilical vein (17 +/- 4 ng/ml) and artery (12 +/- 3 ng/ml) at midgestation increased more than 2-fold by Day 170. The estimated secretion rate of placental progesterone into the fetus was similar at mid- (752 +/- 154 ng/min) and late (681 +/- 171 ng/min) gestation, whereas that for 20 alpha-OHP was negligible at midgestation (57 +/- 71 ng/min) and increased 15-fold (p < 0.05) by term (892 +/- 241 ng/min). Because 20 alpha-OHP is a metabolite of progesterone, total placental progesterone production was greater (p < 0.05) at term (1595 +/- 400 ng/min) than at midgestation (809 +/- 171 ng/min). This study demonstrates that placental secretion of progesterone is bidirectional whereas that of 20 alpha-OHP occurs selectively into the fetus. Although progesterone and 20 alpha-OHP levels in the fetus were lower at term than at midgestation, because of the developmental increase in umbilical blood flow as determined by others, placental progesterone production was actually increased during this interval. Therefore, we suggest that the estrogen-dependent developmental increase in key components of the progesterone biosynthetic pathway, recently demonstrated by us in the baboon placenta, is associated with a corresponding increase in progesterone production.

The neuroactive steroid 3 alpha-hydroxy-5 beta-pregnan-20-one is a two-component modulator of ligand binding to the GABAA receptor

Neuroactive steroids allosterically inhibit [35S]t-butylbicyclophosphorothionate ([35S]TBPS) and enhance [3H]flunitrazepam binding to the GABAA receptor complex. In the presence of 5 microM GABA, 3 alpha-hydroxy-5 beta-pregnan-20-one (3 alpha, 5 beta-P) inhibits [35S]TBPS binding with high- (IC50 21-32 nM) and low- (IC50 24-63 microM) affinity components in bovine cortical, cerebellar, and hippocampal membranes. The percentage of high-affinity sites ranges from 53% in cortex to 65% in cerebellum and hippocampus. However, 3 alpha, 5 beta-P is a single-site inhibitor in thalamus (IC50 43 nM). In the absence of GABA, similar affinities for the high- and low-affinity components were detected, although the percentages of high-affinity sites were reduced. Similarly, 3 alpha, 5 beta-P enhances [3H]flunitrazepam binding with high- (EC50 44-58 nM) and low- (EC50 2-13 microM) affinity components which account for 71-77% and 23-29% of the sites, respectively, in cortex, cerebellum and hippocampus. 3 alpha, 5 beta-P is a single-site enhancer in thalamus (EC50 80 nM). In contrast to 3 alpha,5 beta-P, 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha,5 alpha-P) is a single site modulator of [35S]TBPS and [3H]flunitrazepam binding in all regions examined. These data provide pharmacological evidence consistent with receptor heterogeneity for neuroactive steroids.

Male preference for the odors of estrous female mice is enhanced by the neurosteroid 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP)

The effects of the centrally produced allylic neurosteroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), on the responses of male mice to the odors of estrous female mice were examined in an odor preference test. Control untreated mice displayed a significant preference for the odors of an estrous female, spending more time in a Y-maze in the vicinity of the odors of an estrous than a non-estrous female. Intracerebroventricular (i.c.v.) administrations of 3 alpha HP enhanced male preference for the odors of estrous females, causing a significant dose-related (0.01-1.0 microgram) increase in the amount of time spent in the proximity of the odors of the estrous female, while having no significant effect on the responses to the non-estrous female odors. These effects of 3 alpha HP were stereospecific, with the stereoisomer, 3 beta-hydroxy-4-pregnen-20-one (3 beta HP), having no significant effects on odor preferences. The analgesic, morphine, also had no significant effects on the responses to female odors suggesting that the enhanced preference for estrous female odors were unlikely to be directly due to any analgesic effects of 3 alpha HP. The effects of 3 alpha HP were significantly reduced by peripheral administrations of the GABAA antagonists, bicuculline and picrotoxin, but were unaffected by either the benzodiazepine antagonist, Ro 15-1788, or the opiate antagonist, naloxone. These results suggest that the neurosteroid 3 alpha HP has facilitatory effects on olfactory mediated male sexual interest or motivation that involve interactions with the GABAA receptor.

Reduction of predator odor-induced anxiety in mice by the neurosteroid 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP)

The effects of the centrally produced allylic neurosteroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), on the responses of male mice to an aversive, anxiety-inducing, predator (cat) odor were examined in an odor preference test. Control untreated mice displayed an anxiogenic response to the cat odor, spending a minimal amount of time in a Y-maze in the vicinity of the cat odor. Intracerebroventricular (i.c.v.) administrations of 3 alpha HP had an anxiolytic action, resulting in significant dose-related (0.01-1.0 micrograms) increases in the amount of time spent in the proximity of the cat odor. These anxiolytic effects of 3 alpha HP were stereospecific, with the stereoisomer, 3 beta-hydroxy-4-pregnen-20-one (3 beta HP) having no significant effects on odor preferences. The analgesic, morphine, also had no significant effects on the response to cat odor indicating that the anxiolytic actions of 3 alpha HP were unlikely to be related to any analgesic effects. The effects of 3 alpha HP were significantly reduced by peripheral administrations of the GABAA antagonists, bicuculline and picrotoxin, but were unaffected by either the benzodiazepine antagonist, Ro 15-1788, or the opiate antagonist, naloxone. These results indicate that the allylic neurosteroid 3 alpha HP has anxiolytic actions involving interactions with the GABAA receptor.

Synthesis of the allylic regulatory steroid, 3 alpha-hydroxy-4-pregnen-20-one, by rat granulosa cells and its regulation by gonadotropins

The production of the allylic regulatory steroid 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP) in the rat ovary was examined and compared to progesterone levels through use of specific RIAs that had been validated by capillary gas chromatography-mass spectrometry (GC/MS). Results showed that serum levels of 3 alpha HP are comparable to levels of progesterone at all ages examined. In the 4-day cycling rat, serum levels of 3 alpha HP were highest during diestrus and lowest during proestrus and estrus, while serum FSH levels were highest during proestrus/estrus and lowest during diestrus. Hypophysectomy resulted in decreases in ovarian and serum 3 alpha HP. Treatment of hypophysectomized rats with eCG, but not hCG, increased ovarian and serum 3 alpha HP, while serum progesterone was elevated by treatment with hCG. Ovariectomy resulted in a 55-60% reduction in serum 3 alpha HP, indicating that ovaries are a substantial, but not exclusive, source of 3 alpha HP in serum. As further evidence, cultures of preparations consisting primarily of either granulosa cells or granulosa/theca "shells" produced 3 alpha HP in time-dependent amounts comparable to those of progesterone. Granulosa cells in culture showed a significant increase in accumulation of 3 alpha HP (and progesterone) due to treatment with FSH, but not LH. In contrast to the granulosa-only cell cultures, follicle shells consisting of theca and granulosa cells responded to either LH or FSH treatment with marked increases in 3 alpha HP; increases resulting from combined treatment (FSH + LH) were significantly greater than those due to each hormone alone, but the increases were not additives.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of follicle-stimulating hormone by the gonadal- and neurosteroid 3 alpha-hydroxy-4-pregnen-20-one involves actions at the level of the gonadotrope membrane/calcium channel

We have previously shown that the gonadal- and neurosteroid 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP) suppresses FSH release in cultures of anterior pituitary cells. We undertook exploration of the mechanisms of this suppression by examining the possible sites of 3 alpha HP action in isolated anterior pituitary cells of rats. The specific objective of this study was to determine if 3 alpha HP suppresses FSH by action at the level of the gonadotrope membrane and/or calcium channels. Pituitary cells from adult randomly cycling female rats were precultured for 72 h and then treated for 4 h with 10 nM GnRH and 0.1 nM 3 alpha HP with or without Ca2+ channel agonists or antagonist. In other experiments, cells were treated with BSA-conjugated 3 alpha HP, progesterone, or 3 beta HP (the stereoisomer of 3 alpha HP). Levels of FSH were determined by RIA in media and cells. GnRH-stimulated FSH release and the total FSH (released plus cellular) were significantly suppressed by 3 alpha HP. The Ca2+ ionophore A23187 induced FSH release and 3 alpha HP significantly suppressed both released and total FSH in its presence. In combination with a high dose (100 microM) of the dihydropyridine-sensitive Ca2+ channel antagonist nifedipine, 3 alpha HP suppressed FSH secretion to a greater extent than the antagonist alone. Cellular content of FSH was also decreased by nifedipine (100 microM) and was further suppressed in the presence of 3 alpha HP. The phenylalkylamine-sensitive Ca2+ channel antagonist methoxyverapamil (D600) suppressed GnRH-induced FSH release, and 3 alpha HP significantly potentiated the suppression. Released and cellular FSH were increased by the dihydropyridine-sensitive agonist BAYK 8644, whereas 0.1 nM 3 alpha HP suppressed this agonist-induced FSH to a greater extent than the maximum dose (100 microM) of nifedipine. In order to test for direct action at the level of the gonadotrope membrane, 3 alpha HP was conjugated to BSA (3 alpha HP-BSA) and administered to cultured pituitary cells. The 3 alpha HP-BSA conjugate (but not progesterone-BSA or 3 beta HP-BSA) significantly suppressed release of FSH. The results of the study suggest that 3 alpha HP may be interacting with the Ca2+ channel component of the GnRH signal transduction mechanism; in addition, 3 alpha HP may also suppress FSH release (and possibly synthesis) through direct action at the level of the gonadotrope membrane.

Suppression in gonadotropes of gonadotropin-releasing hormone-stimulated follicle-stimulating hormone release by the gonadal- and neurosteroid 3 alpha-hydroxy-4-pregnen-20-one involves cytosolic calcium

The gonadal- and neurosteroid 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP) suppresses FSH release in cultures of anterior pituitary cells. In a previous report, we showed that this suppression is achieved at least in part by an interaction at the plasma membrane level. We undertook to examine the possible interaction of 3 alpha HP at the level of intracellular Ca2+. Anterior pituitary cells from adult randomly cycling female rats were treated for 4 h with 10 nM GnRH and 0.1 nM 3 alpha HP with or without protein kinase C activator (SC10), antagonist (H-7), intracellular Ca2+ chelator (TMB-8), and intracellular Ca2+ mobilizer (glutamate), and with or without EGTA and Ca2+ in the medium. FSH content in media and cells was determined by RIA. The protein kinase C (PKC) activator, SC10, increased basal levels of secreted FSH. 3 alpha HP suppressed (P < 0.05) SC10-stimulated basal FSH release. The PKC inhibitor, H7, decreased GnRH-induced FSH release; FSH was further suppressed (P < 0.05) by 3 alpha HP in the presence of H7. These results were interpreted to indicate that 3 alpha HP may act in part at the level of PKC and also at another site(s). The intracellular Ca2+ chelator, TMB-8, suppressed released and cellular GnRH-stimulated FSH to the same extent as 3 alpha HP; FSH was not further decreased by 3 alpha HP in the presence of TMB-8. 3 alpha HP suppressed glutamate-stimulated FSH release in Ca(2+)-free medium (P < 0.01). Moreover, GnRH-induced release of FSH was suppressed to the same degree by 10(-10) M 3 alpha HP as by 10(-4) M EGTA. In pituitary cell suspensions, the GnRH-induced [Ca2+]i elevations were significantly (P < 0.05) attenuated by 3 alpha HP. From these and previous results, a model is proposed for the action of 3 alpha HP. The model suggests that 3 alpha HP may interact with gonadotropes at the level of the PKC cell signaling pathway and intracellular Ca2+ mobilization, in addition to the plasma membrane/calcium channel. The interaction effects a decrease in intracellular Ca2+, leading to decreases in FSH release from those pituitary gonadotropes that are responsible for FSH. The consistent decrease in total FSH (released plus cellular content) by 3 alpha HP suggests that this neurosteroid may also suppress FSH synthesis.

General anesthetics potentiate gamma-aminobutyric acid actions on gamma-aminobutyric acidA receptors expressed by Xenopus oocytes: lack of involvement of intracellular calcium

Potentiation of the gamma-aminobutyric acid (GABAA) receptor-gated Cl- channel response has been suggested to be a primary action of some anesthetic agents. We asked whether the GABAA receptor is a target site common for general anesthetics that are chemically and structurally diverse. This hypothesis was tested in Xenopus oocytes expressing mouse cortical mRNA, and GABA-activated Cl- currents were measured using two-electrode voltage clamping. General anesthetics, including inhalational (halothane, diethylether, enflurane and isoflurane), i.v. (3 alpha-hydroxy-5 alpha-dihydroprogesterone, ketamine and propofol) and alcohol (pentanol) anesthetics, enhanced GABA-induced currents by 56 to 1089% at concentrations that were clinically relevant. The results suggest that potentiation of the GABAA receptor/channel response may be a common action for anesthetic agents. Moreover, anesthetic effects were dependent on GABA concentrations; the enhancement was marked with low GABA concentrations and was exponentially decreased as the GABA concentration increased. Also, anesthetic effects were dependent on anesthetic concentrations. The apparent EC50 of halothane was found to be similar to the anesthetic ED50. We also investigated the role of intracellular Ca++ in mediating anesthetic enhancement of the GABA current. We found that intracellular injection of the Ca++ chelator, EGTA, did not change the enhancement by anesthetics. In addition, these anesthetics alone did not produce significant currents, suggesting that the Ca(++)-dependent Cl- current was not activated by these anesthetics per se. Thus, we found that diverse anesthetics potentiate GABA-induced Cl- currents, but this action is not mediated by a release of intracellular Ca++.

A radioimmunoassay for the regulatory allylic steroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP)

The allylic steroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), found in gonadal and brain tissues by radiotracer and chemical methods, had been shown to play a role in gametogenesis, gonadotropin secretion and brain excitability. Since no simple assay was available, a radioimmunoassay for 3 alpha HP was developed using [3H]3 alpha HP and an antiserum raised against 3 alpha HP-20-CMO conjugated to bovine serum albumin. The specificity of the assay for the 3 alpha allylic configuration of 3 alpha HP was confirmed by examining 32 other steroids; cross-reaction with steroids containing different configurations (including metabolites of 3 alpha HP such as progesterone) was less than 0.9%. A Scatchard plot indicated a Ka of 1.56 X 10(9) M-1. Inter- and intra-assay coefficients of variation were 13.1 and 4.5%, respectively. The sensitivity of the assay was 6 pg and the 50% intercept of the standard curve was approx. 123 pg. The measurement by RIA of 3 alpha HP from standard solutions and HPLC purified tissue extracts was confirmed qualitatively and quantitatively by GC/MS methods. The RIA method was employed to determine 3 alpha HP levels in cultured Sertoli cells and in serum of intact and ovariectomized adult rats. Although for most uses, chromatography would not be necessary, two possible methods are presented to enable the separation of 3 alpha HP from other interfering steroids prior to RIA.

Side-chain cleavage of cholesterol sulfate by ovarian mitochondria

Mitochondria isolated from porcine corpora lutea and from the luteinized ovaries of gonadotropin-treated immature rats were found to efficiently cleave the side-chain of cholesterol sulfate to produce 3 beta-hydroxy-5-pregnen-20-one sulfate (pregnenolone sulfate). When mitochondria were preincubated with cholesterol sulfate, the time-course for the side-chain cleavage of cholesterol sulfate was biphasic. With 200 microM cholesterol sulphate, the initial rate of the reaction was the same as that observed for 25-hydroxycholesterol. This rate was not increased when both cholesterol sulfate and 25-hydroxycholesterol were incubated together. The rate of side-chain cleavage by isolated mitochondria supplied with 75 microM cholesterol sulfate as substrate was inhibited by 97% by aminoglutethimide, a specific inhibitor of cytochrome P-450scc. The slow phase of side-chain cleavage of cholesterol sulfate appeared to be limited by the rate of substrate movement to the mitochondrial site of the reaction. Cholesterol sulfate translocation rates were however up to 8 times greater than those observed for cholesterol when equivalent concentrations of the two substrates were added to the mitochondria. We conclude that cholesterol sulfate is a better substrate than cholesterol for side-chain cleavage by isolated mitochondria and that both reactions are catalysed by the same cytochrome P-450scc enzyme.

Characterization of steroid interactions with gamma-aminobutyric acid receptor-gated chloride ion channels: evidence for multiple steroid recognition sites

The potentiation of gamma-aminobutyric acid (GABA) receptor-mediated 36Cl- uptake by various steroids has been characterized in rat cerebral cortical synaptoneurosomes. Several of these steroids, including 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha-OH-DHP) and 3 alpha,21-dihydroxy-5 alpha-pregnan-20-one (THDOC), increase the potency of muscimol to stimulate 36Cl- uptake in a concentration-dependent and stereospecific manner. Concentration-response curves for 3 alpha-OH-DHP, THDOC, 3 alpha-hydroxy-pregn-4-en-20-one, and pentobarbital enhancement of muscimol-stimulated 36Cl- uptake are biphasic, with Hill coefficients significantly less than 1.0. Computer-modeling (ALLFIT analysis) of these curves suggests that these steroids and pentobarbital interact with multiple binding sites on GABAA receptor(s). In contrast, the concentration-response curve for THDOC 21-mesylate is monophasic, with a smaller maximal response, and yields a Hill coefficients of 1.0. In addition to modulating GABA receptor-mediated 36Cl- uptake, THDOC enhanced the ability of the benzodiazepine clonazepam to potentiate muscimol-stimulated 36Cl- uptake. The central benzodiazepine antagonist Ro15-1788 failed to inhibit THDOC-induced potentiation of muscimol-stimulated 36Cl- uptake, although it has been previously reported to inhibit some of the behavioral actions of THDOC. In contrast to the A ring-reduced metabolites and analogues of progesterone and deoxycorticosterone, glucocorticoids had no effect on muscimol-stimulated 36Cl- uptake in cerebral cortical synaptoneurosomes at concentrations between 20 nM and 5 microM.

Selective suppression of follicle-stimulating hormone secretion in anterior pituitary cells by the gonadal steroid 3 alpha-hydroxy-4-pregnen-20-one

The effect of 3 alpha-hydroxy-4-pregnen-20-one (3HP), a Sertoli cell steroid, on the secretion of gonadotropins from rat anterior pituitary cells in culture was examined and subsequently compared with the action of other gonadal steroids and steroids structurally related to 3HP. Pituitary cells from randomly cycling, sexually mature female rats were isolated and maintained in culture 72 h before use. On the day of treatment, medium was changed, steroids (10(-16)-10(-4) M) and/or LHRH (10(-8) M) were added, and cells were allowed to incubate for a further 24 h. Medium was then examined for gonadotropin content by RIA. 3HP treatment of anterior pituitary cells resulted in a significant reduction of both basal and LHRH-induced FSH secretion, while LH secretion was unaffected. The lowest effective dose of 3HP (10(-16) M) significantly decreased basal FSH secretion to 65.6% of control levels. The lowest effective dose of 3HP that significantly inhibited (by 31%) LHRH-induced FSH secretion was 10(-14) M 3HP. Maximum suppression by 3HP of basal FSH secretion occurred between 10(-10)-10(-8) M, and maximum suppression of LHRH-induced secretion occurred at 10(-12) M. None of the other gonadal steroids tested (progesterone, testosterone, 5 alpha-dihydrotestosterone, 17 beta-estradiol, 20 alpha-hydroxy-4-pregnen-3-one, and 5 alpha-pregnane-3,20-dione) had a similar selective effect on FSH secretion; progesterone, testosterone, and 17 beta-estradiol actually resulted in increased FSH release, and 5 alpha-pregnane-3,20-dione resulted in significant increase in basal LH. A number of metabolites and structural variations of 3HP were examined in this in vitro system at concentrations of 10(-12)-10(-6) M, and none exhibited a similar selective FSH-suppressing activity as 3HP. The data suggest that the selective FSH-suppressing effect of 3HP seen previously in vivo and here in vitro is due to 3HP itself and not the result of a metabolite of this molecule.

Influence of A23187 and dibutyryl cyclic AMP on progestagen production by rat granulosa cells in vitro

The gonadotrophic regulation of progesterone production by rat granulosa cells was examined in a chemically-defined medium containing FSH, dibutyryl cyclic AMP [Bu)2cAMP) and the calcium ionophore, A23187. FSH and A23187 alone significantly enhanced the production of pregnenolone, progesterone and its metabolite, 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OH-P) from endogenous substrate(s). Stimulation of progesterone production by A23187 was accompanied by an increase in 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) but not 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) activity, as attested by enhancement of the metabolism of exogenous pregnenolone to progesterone but not of progesterone to 20 alpha-OH-P. In contrast, although (Bu)2cAMP increased pregnenolone and progesterone production and the metabolism of exogenous progesterone to 20 alpha-OH-P, it failed to stimulate the conversion of exogenous pregnenolone to progesterone. The increase in progesterone production and in the conversion of exogenous pregnenolone to progesterone by FSH and A23187 was concentration- and time-dependent. Whereas maximal stimulation of de-novo progesterone synthesis by FSH was evident by 6 h (earliest time examined), a significant increase in the conversion of exogenous pregnenolone to progesterone in the presence of FSH or the ionophore was not noted until 12 h of incubation. Although a small but significant increase in progesterone production was also noted as early as 6 h of incubation in the presence of the calcium ionophore, this was markedly smaller than that elicited by FSH. We conclude that the calcium ionophore A23187 and (Bu)2cAMP have similar as well as distinct effects on progesterone production in rat granulosa cells in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of spermatocyte development in prepubertal rats by the Sertoli cell steroid, 3 alpha-hydroxy-4-pregnen-20-one

The effect of 3 alpha-hydroxy-4-pregnen-3-one (3HP), a Sertoli cell steroid, on spermatogenesis was examined in normal and gonadotropin-suppressed rats, through s.c. as well as direct intratesticular injections. Early experiments employing normal prepubertal male rats indicated that 3HP, when administered at 65 micrograms/100 g BW daily for 15 days, was capable of stimulating pachytene spermatocyte number to 149% of untreated control numbers. It was of interest to determine if this effect could be amplified in gonadotropin-suppressed animals. Neonatally estrogenized rats (500 micrograms estradiol benzoate in 0.1 ml oil at 2 days) were treated on alternate days with 3HP (100 micrograms/100 g BW) for 3 wk, starting at 7 days of age. This treatment significantly increased the number of spermatocytes per tubule cross section from 17.3 +/- 1.9 (in estradiol benzoate-only animals) to 47.1 +/- 7.9 (p less than 0.01). In a similar study, 100 micrograms/100 g BW of testosterone propionate could stimulate spermatocyte number to only 15.1 +/- 2.2 cells per tubule cross section versus estradiol benzoate-only numbers. A single intratesticular injection of 3HP (2 ng in 2.0 microliters oil) in Methallibure-treated rats resulted in a significant increase in late pachytene spermatocyte numbers from 0.77 +/- 0.12 in Methallibure-only-treated rats to 1.70 +/- 0.10 (p less than 0.001) cells per tubule cross section in 28-day-old rats. However, in this study, no other progesterone metabolite or androgenic steroid (testosterone, 5 alpha-dihydrotestosterone, or 5 alpha-androstan-3 alpha, 17 beta-diol) tested was capable of this level of germ cell stimulation. In conclusion, 3HP appears to have a direct effect on germ cell development within the testis at levels much lower than those shown to be effective for androgens. It does not appear that this effect is mediated through the conversion of 3HP to any C21 or C19 steroids, and appears to be the first report of a Sertoli cell steroid with a possible role in the process of mammalian spermatogenesis.

Gamma-interferon inhibits rat granulosa cell differentiation in culture

A growing body of evidence indicates that factors secreted by cells of the immune system can directly affect a variety of endocrine phenomena. In the present study we examined the direct effects of the cytokine, interferon (IFN), on FSH-stimulated steroidogenesis and LH/hCG receptor induction in rat granulosa cells. We show that gamma-IFN, but not alpha-IFN, inhibits FSH-stimulated progesterone, 20 alpha-hydroxypregn-4-en-3-one and estrogen production as well as gonadotropin-induced LH/hCG receptor formation in a dose-dependent manner. The results suggest that gamma-IFN may play a role in the maturation and differentiation of granulosa cells and thus may serve as a regulatory link between the immune and reproductive endocrine systems.

Analgesic effects of the putative FSH-suppressing gonadal steroid, 3 alpha-hydroxy-4-pregnen-20-one: possible modes of action

The effects of intracerebroventricular (i.c.v.) administrations of the putative follicle stimulating hormone (FSH) suppressing gonadal steroid, 3 alpha-hydroxy-4-pregnen-20-one (3A4P) on the nociceptive responses of male mice were examined. This allylic steroid elicited significant, dose-dependent (0.001-1.0 micrograms) analgesic responses for 90-150 min after injection. These analgesic effects of 3A4P were stereospecific, the stereoisomer, 3 beta-hydroxy-4-pregnen-20-one (3B4P) failing to affect the nociceptive responses. The analgesic effects of 3A4P were blocked by peripheral administrations of the GABA antagonists, bicuculline and picrotoxin, and reduced by the benzodiazepine antagonist, Ro 15-1788. The exogenous opiate antagonist, naloxone, and the putative endogenous opioid antagonist, Tyr-MIF-1 (Pro-Leu-Gly-amide), also reduced 3A4P-induced analgesia, while i.c.v. administration of 3A4P (0.001 and 0.01 micrograms) itself attenuated the analgesic effects arising from peripheral administrations of opiate receptor agonist, morphine. In addition, the calcium channel antagonists, nifedipine and verapamil, enhanced 3A4P-induced analgesia but had no evident effects on the actions of 3B4P. These results suggest that the central analgesic effects of the FSH-suppressing steroid, 3A4P, arise via benzodiazepine--GABA--opiate mechanisms and calcium channels. These findings also suggest possible central modes of action whereby 3A4P may elicit selective suppression of FSH.

Selective suppression of follicle-stimulating hormone by 3 alpha-hydroxy-4-pregnen-20-one, a steroid found in Sertoli cells

Previous reports have not identified a naturally occurring steroid that selectively inhibits FSH secretion without also inhibiting LH secretion. The effect of 3 alpha-hydroxy-4-pregnen-20-one (3-HP), a steroid produced in Sertoli cells, on gonadotropin secretion in intact and castrate male and female, prepubertal and adult rats and in cultures of anterior pituitary cells was investigated. Intact prepubertal male rats were treated with a single sc injection of 0.2 mg/kg 3-HP, and castrate male and female rats were given a daily sc injection of 0.2 mg/kg 3-HP for 4 days. Serum FSH levels were suppressed by 26-44% (P less than 0.001-0.05), with no similar effect on serum LH levels. The acetyl derivative of 3-HP (3-HPA), administered to castrate prepubertal and adult rats for 4 days (0.625 mg/kg), resulted in significant decreases (P less than 0.001) in serum FSH to 45% and 19% of castrate control levels, respectively, without a significant effect on LH levels. Treatment of castrate prepubertal male rats with various doses of 3-HPA (0.001-0.625 mg/kg X day) for 4 days resulted in a dose-related suppression of serum FSH. Similar results were obtained with chronic (14-day) treatment of intact male rats with 3-HPA. Treatment of young (15-day-old) intact males with either 3-HP or 17 beta-hydroxy-5 alpha-androstan-3-one (DHT) for 14 days showed that DHT resulted in significant increases in prostate and seminal vesicle weights, while 3-HP showed no apparent androgenic activity. The effects of treatment with 3-HP, 3 beta-HP, 17 beta-estradiol, and DHT (0.025-0.625 mg/kg X day) were compared. Treatment with 3 beta-HP resulted in significant increases in serum FSH levels; 17 beta-estradiol and DHT suppressed both gonadotropins (at the higher doses administered), while 3-HP suppressed only FSH. 3-HP (3.16 X 10(-11) M) and/or LHRH (3 X 10(-8) M) were employed in primary cultures of anterior pituitary cells. Addition of LHRH resulted in 6- to 8-fold increases in the secretion of FSH and LH, while 3-HP suppressed basal (P less than 0.05) and LHRH-stimulated (P less than 0.001) FSH secretion by 26% and 77%, respectively. We conclude that 3-HP selectively suppresses FSH secretion and may be involved in the normal regulation of FSH secretion in the male.

Steroid hormone metabolites are barbiturate-like modulators of the GABA receptor

Two metabolites of the steroid hormones progesterone and deoxycorticosterone, 3 alpha-hydroxy-5 alpha-dihydroprogesterone and 3 alpha, 5 alpha-tetrahydrodeoxycorticosterone, are potent barbiturate-like ligands of the gamma-aminobutyric acid (GABA) receptor-chloride ion channel complex. At concentrations between 10(-7) and 10(-5)M both steroids inhibited binding of the convulsant t-butylbicyclophosphorothionate to the GABA-receptor complex and increased the binding of the benzodiazepine flunitrazepam; they also stimulated chloride uptake (as measured by uptake of 36Cl-) into isolated brain vesicles, and potentiated the inhibitory actions of GABA in cultured rat hippocampal and spinal cord neurons. These data may explain the ability of certain steroid hormones to rapidly alter neuronal excitability and may provide a mechanism for the anesthetic and hypnotic actions of naturally occurring and synthetic anesthetic steroids.

17alpha-Ethyl-20alpha-and -20beta-dihydroprogesterones and other 17alpha-ethyl-substituted pregnanes as potential contragestational agents

The 17alpha-ethyl-substituted analogs of the two epimeric 20-dihydroprogesterones, allopregnadedione and pregn-5-ene-3,20-dione, were synthesized and evaluated for their possible oral contragestational (postcoital antifertility) activity in the rat. The compounds, though bound strongly to the progesterone receptor in vitro, were inactive preimplantively at 10 mg/kg and postimplantively at 40 mg/kg in vivo.

[Modulation of 17-alpha-hydroxy-20 beta-dihydroprogesterone or gonadotropic extract activity on the in vitro intrafollicular maturation of rainbow trout (Salmo gairdnerii) oocytes by various steroids lacking maturing activity]

The efficiency of 17 alpha-hydroxy-20 beta-dihydroprogesterone (17 alpha-20 beta Pg) or of a Trout pituitary gonadotropic extract to induce intrafollicular maturation of trout oocytes can be modulated by some steroids which do not present any direct maturing action: gonadotropic extract efficiency is lowered by estradiol and estrone, and enhanced by testosteron. As these steroids do not present a significant effect on 17 alpha-20 beta Pg induced maturation, their site of action may be located in the follicular tissues. The corticosteroids, particularly cortisol and cortisone enhance the maturing efficiency of gonadotropin and stimulate much more strongly the efficiency of 17 alpha-20 beta Pg. This suggests a direct effect on oocyte sensitivity to 17 alpha-20 beta Pg.

Microdetermination of progestins in rat ovaries: progesterone and 20 alpha-hydroxy-pregn-4-en-3-one content during proestrus, oestrus and pseudopregnancy

A method is described for the determination of progesterone (P) and 20α-hydroxy-pregn-4-en-3-one (20αOHP) in rat ovaries by combined paper- and vapour-phase chromatography. In pseudopregnant rats during the 4th to 7th day of leucocytic vaginal smear, the progesterone content of a pair of ovaries varied about a mean of 1 μg, and the ratio P/20αOHP ranged from 2.2 to 3.0. The ovarian progesterone content was minimal (0.15 μg/pair) on the morning of prooestrus, rose significantly on the afternoon of prooestrus (0.4 μg) and declined again before the morning of oestrus. Throughout dioestrus, prooestrus and oestrus the ovarian content of 20αOHP exceeded that of progesterone (P/20αOHP = 0.27–0.51). This inversion of the P/20αOHP ratio reflects the increase in ovarian 20α-hydroxysteroid dehydrogenase activity known to occur during follicular proliferation. Cyclic changes observed in the content of progestins in the ovaries, including the preovulatory rise, parallel those previously described in ovarian venous blood.

Effect of ergocornine on ovarian synthesis of progesterone and 20 alpha-hydroxy-pregn-4-en-3-one in the pseudopregnant rat

The ovarian content of progesterone (P) and 20α-hydroxy-pregn-4-en-3-one (20αOHP) was measured in rats given a subcutaneous injection of 1 mg ergocornine methanesulphate (ECO) on day L4 of pseudopregnancy and in untreated pseudopregnant controls. The progesterone content in the ovaries of the treated rats declined, after a latency of 12 h, to 44% of the control level at 24 h, and to 30% at 30 to 72 h after the ECO injection. This fall in progesterone level coincided with a sharp rise in 20αOHP content of the ovaries and consequent inversion of the P/20αOHP ratio, from 1.9–3.8 in the controls to 0.24–0.45 in the ECO-treated rats. The total P + 20αOHP content of the ovaries remained similar in treated and control rats, except for a significant fall 48 h after ECO injection. The changes in ovarian steroid content after ECO administration mimic those observed during spontaneous prooestrus and oestrus and account for the interruption of the progestational state brought about by the drug. The results negate the postulate that ECO exerts its pregnancy-interrupting action in the rat by direct inhibition of ovarian 3β-hydroxysteroid dehydrogenase and are consistent with the view that this action of the drug is mediated by suppression of prolactin secretion by the pituitary gland; such a suppression may be secondary to an excitatory effect on the hypothalamus.