Showing papers on "Pregnenolone published in 1976"
TL;DR: Results in pre-pubertal girls and women in the follicular phase of the menstrual cycle suggest that the major change in adrenal steroid production at puberty may be an increase in 17, 20-desmolase activity.
277 citations
TL;DR: It is suggested that during sexual maturation the testicular biosynthesis of active 5-ane androgens may proceed via5-ane precursors with the help of age-dependent 5-anes-3beta-hydroxysteroid dehydrogenase activities.
Abstract: The activities of hydroxysteroid dehydrogenases of 5-ane and 5-ene steroids were examined in interstitial tissue from testes of rats at different ages. The enzyme reactions were localized in the Leydig cell cytoplasm of isolated cells and in frozen tissue slices. Relative reaction velocities of the NADlinked hydroxysteroid dehydrogenases were obtained spectrophotometrically with 17 steroid substrates using the 12,000 i g supernatant of isolated interstitial cells from 28–29 clay old rats; the rate of 3(α,β) dehydrogenation of 5-ane-3β steroids was markedly (10 to 20i) higher than that of 5-ene-3β steroids and 5-ane-3α steroids. The hydroxysteroid dehydrogenase activities of testes from 124 rats between the ages of 15 and 138 days were determined using as substrates, 3β-hydroxy- 5β-androstan-17-one, 3β-hydroxy-5a-androstan- 17-one, 3β,17β-dihydroxy-5α-androstane, dehydroepiandrosterone and pregnenolone. Between the ages of 15 and 32 or 34 days the gonads grow in size more rapidly than the body and the 5-an...
144 citations
TL;DR: Serum concentrations of these steroids are given for women in the follicular and luteal phases of the menstrual cycle and for women on oral contraceptives of the combination type, as well as for normal men.
Abstract: We describe a method for determination of pregnenolone, progesterone, 17alpha-hydroxyprogesterone, testosterone, and 5alpha-dihydrotestosterone in 1-2 ml of serum from male or female. Using microcolumns of Lipidex-5000 (hydroxyalkoxypropyl Sephadex, 0.5 g) and light petroleum/chloroform (97/3) as the solvent during chromatography, we resolved these five steroids into four fractions, with pregnenolone and 5alpha-dihydrotestosterone eluting together. By use of selected antibodies, the latter two steroids were also determined specifically. Use of microcolumns allowed minimization of solvent volumes and sample transfers. Consequently, blank values for all the five steroids were negligible. Lowest measureable concentrations (in ng/liter) were: pregnenolone 100, progesterone 25, 17alpha-hydroxyprogesterone 50, testosterone 25, and 5alpha-dihydrotestosterone 25. Intra-assay and inter-assay coefficients of variation ranged from 5 to 9% and 10 to 15%, respectively, for the five steroids. Serum concentrations of these steroids are given for women in the follicular and luteal phases of the menstrual cycle and for women on oral contraceptives of the combination type, as well as for normal men.
127 citations
TL;DR: The results suggest the sequence A leads to B leads to C leads to D as the basic mechanism for the conversion of cholesterol to pregnenolone as the initial process involving an initial oxygen attack of cholesterol at C-22.
100 citations
TL;DR: Analysis of kinetic data and the effects of different buffers and of Miranol H2M suggested that estrone sulfatase and arylsulfatase C are identical but that they are distinct from the other sulfatases.
88 citations
TL;DR: Biochemical evidence demonstrates that the A5-3(3-hydroxysteroid oxydoreductase activity is solely localized in the follicular envelopes, and evidence is presented which strongly suggest that the conversion of pregnenolone to progesterone is a prerequisite for biological activity.
Abstract: Ovarian follicles of Xen opus laevis exposed to exogenous radioactive pregnenolone have been observed to synthesize radioactive progesterone. Biochemical evidence demonstrates that the A5-3(3-hydroxysteroid oxydoreductase activity is solely localized in the follicular envelopes. Cyanoketone inhibits HCG induced maturation and also pregnenolone-induced maturation. Evidences are presented which strongly suggest that the conversion of pregnenolone to progesterone is a prerequisite for biological activity. Progesterone and related steroids are actively metabolized by the ovarian follicle and also by the isolated (after collagenase treatment) oocyte. The results demonstrate that the defolliculated oocyte possess a 17tr-hydroxylase, a C21.19 desmolase, a 20o-hydroxysteroid oxydoreductase and 5j3/0-reductases. The two main metabolites isolated, after exposure to progesterone, from the oocyte are androstenedione and 1 7n, 20o-dihydroxy-p regn-4-ene-3-one.
59 citations
TL;DR: A marked lack of mitochondrial specificity towards the steroid side chains is in direct contrast with the rat liver microsomal cholesterol 7alpha-hydroxylase, which has a high specificity for the side chain.
Abstract: The rate of oxidation of cholesterol and its analogues to pregnenolone (3beta-hydroxypregn-5-en-20-one) by various mitochondrial preparations was measured. Sterols with the cholest-5-en-3beta-ol ring system and saturated side chains of different lengths were converted into pregnenolone rat rates similar to that of cholesterol. This marked lack of mitochondrial specificity towards the steroid side chains is in direct contrast with the rat liver microsomal cholesterol 7alpha-hydroxylase, which has a high specificity for the side chain. Steroids that retain the ring system, but contain hydroxyl groups at various points in the side chain, are converted into pregnenolone at rates three to eight times higher than in cholesterol. The results are discussed with reference to current ideas on the mechanism of the side-chain cleavage of cholesterol. The results are discussed with reference to current ideas on the mechanism of the side-chain cleavage of cholesterol.
55 citations
TL;DR: Differences were observed in the times of oviposition of eggs which ovulated in response to injections of either progesterone or a corticosteroid and it was suggested that the mechanism of action of progestersone and corticosterone operates through different endocrine pathways.
Abstract: 1. Pregnenolone, progesterone, deoxycorticosterone and cortico‐sterone were injected into hens between 16.30 and 17.00 h on the day of oviposition of the last egg of a sequence. 2. Pregnenolone did not affect ovulation, but all of the other steroids induced ovulation prematurely. 3. To induce premature ovulation in 50% of the hens, 82–31 μg± 0.06 μg, 23–86 μg±0.07 μg and 659–26 μg + 0.05 μg of progesterone, deoxycorticosterone and corticosterone, respectively were required for injection. 4. Differences were observed in the times of oviposition of eggs which ovulated in response to injections of either progesterone or a corticosteroid and it was suggested that the mechanism of action of progesterone and corticosteroids operates through different endocrine pathways.
50 citations
TL;DR: Estrone sulfatase activity was inhibited noncompetitively by sulfate esters of dehydroepiandrosterone, pregnenolone, and cholesterol; on the other hand, other steroid sulfatases were inhibited by these latter three sulfates competitively.
Abstract: – The enzymatic hydrolysis by brain homogenate of the sulfate esters of estrone, pregnenolone, dehydroepiandrosterone, testosterone, cholesterol and p-nitrophenol was studied. With homogenate of young rat brain, the pH optima of estrone sulfatase4 and arysulfatase C (p-nitrophenyl sulfate as substrate) were 8.2 and all other steroid sulfatases had pH optima at 6.6. Apparent Kms for these steroid sulfates were widely different. The highest Km value was 32.2 μm for estrone sulfate and the lowest was 0.66 μm for testosterone sulfate; the Km for p-nitrophenyl sulfate was 30 fold higher than for estrone sulfate. Specific activity was also highest with estrone sulfatase and lowest with testosterone sulfatase; specific activity with aryl sulfatase C was over 3 fold higher than with estrone sulfatase. Estrone sulfatase activity was inhibited noncompetitively by sulfate esters of dehydroepiandrosterone, pregnenolone, and cholesterol; on the other hand, other steroid sulfatases were inhibited by these latter three sulfates competitively. Developmental changes of these sulfohydrolase activities in rat brain were almost identical with the exception of testosterone sulfatase activity; the latter sulfatase had a peak activity at 30 days old, while all other sulfatase had a peak at 20 days old. Thermal stability of all these activities was identical. Testosterone sulfatase activity in neurological mouse mutants, jimpy, msd, and quaking mice, was less than one half of littermate controls, while other steroid sulfatase levels in these mutants' brain were normal. All sulfatase activities were diminished in the brain of a metachromatic leukodystrophy patient with multiple sulfatase deficiency. The brains of classical metachromatic leukodystrophy patients contained normal levels of all steroid sulfatases and arylsulfatase C, with the single exception of testosterone sulfatase which level was less than 50% of control.
49 citations
TL;DR: The results indicate that whenever both blood and semen are analysed, blood sampling must precede semen collection, because the plasma levels of all steroids were significantly increased after masturbation, whereas steroid levels remained unchanged in the control study.
Abstract: The levels of pregnenolone, dehydroepiandrosterone (DHA), androstenedione, testosterone, dihydrotestosterone (DHT), oestrone, oestradiol, cortisol and luteinizing hormone (LH) were measured in the peripheral plasma of a group of young, apparently healthy males before and after masturbation. The same steroids were also determined in a control study, in which the psychological antipation of masturbation was encouraged, but the physical act was not carried out. The plasma levels of all steroids were significantly increased after masturbation, whereas steroid levels remained unchanged in the control study. The most marked changes after masturbation were observed in pregnenolone and DHA levels. No alterations were observed in the plasma levels of LH. Both before and after masturbation plasma levels of testosterone were significantly correlated to those of DHT and oestradiol, but not to those of the other steroids studied. On the other hand, cortisol levels were significantly correlated to those of pregnenolone, DHA, androstenedione and oestrone. In the same subjects, the levels of pregnenolone, DHA, androstenedione, testosterone and DHT, androstenedione and oestrone. In the same subjects, the levels of pregnenolone, DHA, androstenedione, testosterone and DHT in seminal plasma were also estimated; they were all significantly correlated to the levels of the corresponding steroid in the systemic blood withdrawn both before and after masturbation. As a practical consequence, the results indicate that whenever both blood and semen are analysed, blood sampling must precede semen collection.
41 citations
TL;DR: Results of the study strongly supported a functional role for placental cytochrome P-450 in the aromatization reaction and a large number of foreign organic compounds which produced type-I binding spectra in rat liver microsomes exhibited either no or very minimal binding.
TL;DR: A steroid sulphotransferase (EC 2.8.2) was partially purified from female rat liver and appeared to be highly susceptible to product inhibition by adenosine 3′,5′diphosphate.
Journal Article•
TL;DR: The above described findings show that the sex differences in steroids secretion by the rat adrenal are partially conditioned by a cholesterol sidechain cleavage activity.
Abstract: In rats postpubertal orchiectomy results in an increase in the adrenal weight, testosterone replacement restores the adrenal weight to the normal level. Neither ovariectomy (8 weeks of duration) nor estradiol replacement has an effect on adrenal weight in female rats. Pregnenolone synthesis as well as corticosterone and blue tetrazolium-positive steroids secretion is significantly higher in homogenates of adrenals from female rats than from males. Orchiectomy results in a marked increase in pregnenolone biosynthesis, testosterone replacement restores the value to the normal levels. Neither ovariectomy nor estradiol replacement has an effect on pregnenolone synthesis in v i t r o. In both sexes gonadectomy causes a marked decrease in corticosterone output by adrenal homogenates, concomitantly the increase in the adrenal 5alpha-reductase activity is observed. The ratio of secreted corticosterone to pregnenolone is significantly lower in gonadectomized rats of both sexes than in control animals. Estradiol or testosterone replacement inhibits the adrenal 5alpha-reductase activity and restores the corticosterone output as well as corticosterone/pregnenolone ratio to the normal values. The above described findings show that the sex differences in steroids secretion by the rat adrenal are partially conditioned by a cholesterol sidechain cleavage activity. Testosterone inhibits this activity while estradiol under applied experimental conditions has no effect on the cholesterol sidechain cleavage activity.
TL;DR: Findings indicate limited adrenal responsiveness to ACTH following chronic glucocorticoid treatment of congenital adrenal hyperplasia, even in under-treated patients, and suggest that normal precursor steroid levels in plasma and normal 17-ketosteroid and pregnanetriol excretion can only be achieved by the suppression of total steroidogenesis to less than that occurring in normal subjects.
Abstract: Both pregnenolone and 17-OH-pregnenolone were found to be higher in the plasma of patients with poorly controlled congential adrenal hyperplasia than in normal subjects. The plasma levels of these precursor steroids were significantly correlated with urinary 17-ketosteroid and pregnanetriol excretion and with plasma testosterone. The mechanism where by plasma pregnenolone and 17-OH-pregnenolone levels are elevated in patients with 21-hydroxylase deficiency is unknown, but the phenomenon of product inhibition is suggested as a possible explanation. As 17-OH-pregnenolone in plasma is almost entirely of adrenal origin, its measurement promises to be useful in the management of patients with congenital adrenal hyperplasia. Acute stimulation with ACTH caused negligible changes in the plasma levels of pregnenolone and 17-OH-pregnenolone and failed to distinguish between overly, appropriately, and under-treated patients. However, following repeated stimulation with repository ACTH, the steroid levels rose. These findings indicate limited adrenal responsiveness to ACTH following chronic glucocorticoid treatment of congenital adrenal hyperplasia, even in under-treated patients, and suggest that normal precursor steroid levels in plasma and normal 17-ketosteroid and pregnanetriol excretion can only be achieved by the suppression of total steroidogenesis to less than that occurring in normal subjects.
TL;DR: Several formulations for the physiological role of I in the oxidative side-chain cleavage of cholesterol to pregnenolone were proposed in the light of these findings.
TL;DR: Stimulation with ACTH for 5 days increased fluorogenic steroid production and induced morphologic changes in both adrenal cell forms, similar to ACTH-stimulated adrenal glands in vivo.
Abstract: Adrenocortical cells obtained from adult rats were propagated in monolayer culture. Depending on culture conditions, they grew either as lipid-containing epithelial-like cells with a high level of steroid production, or as fibroblast-like cells with a low level of steroid production. The major fluorogenic steroid secreted by both morphologic forms of adrenal cortical cell was corticosterone as determined by chromatography and acid fluorometry. Basal fluorogenic steroid production per 10(6) cells over 24 h was: epithelial-like cells, 5.0-mug; fibroblast-like cells, 0-014 mug. Stimulation with ACTH for 5 days increased fluorogenic steroid production and induced morphologic changes in both adrenal cell forms. ACTH stimulation of fluorogenic steroid production by both cell forms reached a maximum after 3 days, then dropped to a refractory state after 5 days. With maximal ACTH stimulation, production increased 25-fold in fibroblast-like cells and five-fold in epithelial-like cells. The latter rate of corticosterone production is similar, per cell, to ACTH-stimulated adrenal glands in vivo. Progressive morphologic changes were observed with ACTH stimulation: epithelial-like cells retracted from the substratum and lost lipid inclusions; fibroblast-like cells became more epithelial-like. Both adrenal cell types formed intermediates from [4-(14)C] pregnenolone including pregn-5-ene-3 phi, 20 alpha-diol and 20 alpha-hydroxy-pregn-4-en-3-one. Control cultures of muscle fascia fibroblasts did not produce corticosterone or intermediates from [4-(14)C[ pregnenolone and did not respond to ACTH functionally or morphologically.
TL;DR: The effects of mammalian and avian gonadotropins on the metabolism of tritiated precursors were studied in this article, showing that the effects of FSH were minimal compared to the same dose of LH.
TL;DR: The identification of pregn-5-ene-3,20-dione, confirmed by mass fragmentography, has provided the first direct evidence for the formation of the hypothetical delta5,3-ketone intermediate in the conversion of pregnenolone to progesterone and suggests that it is possible to inhibit the isomerase to a greater extent than the dehydrogenase.
TL;DR: The effect of Ca2+ in vitro on pregnenolone production rates under various incubation conditions by mitochondrial fractions isolated from testes of normal rats and of rats after in vivo treatment with luteinizing hormone has been investigated.
TL;DR: The results obtained indicate that human breast tumours are capable of converting pregnenolone and dehydroepiandrosterone to progesterone and androstenedione respectively.
TL;DR: In this article, the location of the 2H atom at C-17 has been obtained by transforming the metabolite to androsta-4,16-dien-3-one and then torost-4-ene-3,17-dione.
TL;DR: Irrespective of the incubation conditions, pregnenolone produced more Δ5-3β-hydroxy-thanΔ4-3-ketosteroids, suggesting a predominance of the former biosynthetic pathway, and among the unidentified metabolites, water-soluble compounds were formed from both precursors in intact tissue incubates.
TL;DR: As no single enzyme is known to catalyze the transfer of hydride-ion to both sides of NAD+, it is proposed that there are at least two 3beta-hydroxysteroid dehydrogenases in the Triton X-100 extract.
TL;DR: Hamster eggs at various developmental stages were studied histochemically fro the presence of delta5-3beta-hydroxysteroid dehydrogenase, which was absent from ovarian eggs but was demonstrated in unfertilized and fertilized eggs up to the blastocyst stage.
Abstract: The presence of delta (5) -3beta-hydroxysteroid dehydrogenase (HSD) with pregnenolone as the substrate and NAD as the cofactor 20alpha-HSD (20alpha-hydroxypregn-4-en-3-one and NADP) and 20beta-HSD (20beta-hydroxypregn-4-en-3-one and NAD) in hamster eggs at various stages of development was investigated histochemically. These enzymes were not detectable in ovarian eggs but were found in unfertilized and fertilized eggs up to the blastocyst stage. There were only slight variations in their activities.
TL;DR: It is indicated that cortisol and androgens are principally synthesized through the so called Δ5 pathway.
TL;DR: A new assay for the measurement of steroid 17alpha-hydroxylase activity in beef adrenals is described, based on the biochemical mechanism of the enzymic reaction, i.e. the direct and stereospecific substitution of the proton located on the hydroxylated position.
Abstract: A new assay for the measurement of steroid 17alpha-hydroxylase activity in beef adrenals is described. This method is based on the biochemical mechanism of the enzymic reaction, i.e. the direct and stereospecific substitution of the proton located on the hydroxylated position. Progesterone or pregnenolone specifically labelled on the 17 position are solubilized in the incubation mixture with the help of Tween 80 and incubated under optimal conditions. The tritium enzymically released from the substrate is found in the medium as a molecule of water which is then distilled under reduced pressure and counted by liquid scintillation. The results obtained with this new method are comparable with those obtained with a conventional method using a 14C-labelled substrate.
TL;DR: Labor was associated with a significant increase in UA levels of DHEA-S and a smaller, but not quite significant, increase inUA levels of delta5P-S, while similar changes for unconjugated delta5-3beta-hydroxysteroids were not observed, and mean A-V gradients between the group of patients in labor and those not in labor were not significantly different.
Abstract: Concentrations of pregnenolone (Δ5P), dehydroepiandrosterone (DHEA), 16α-hydroxydehydroepiandrosterone (16α-OH DHEA), pregnenolone sulfate (Δ5P-S), and dehydroepiandrosterone sulfate (DHEA-S) were measured simultaneously by radioimmunoassay in individual, paired umbilical artery (UA) and vein (UV) sera from 18 normal term pregnancies, 6 in labor, 12 not in labor. Mean UA and UV levels ± SEM (ng/ml) were for Δ5P: 30.39 ± 1.69, 35.55 ± 3.06; DHEA: 12.31 ± 2.34, 3.66 ± 0.38; 16α-OH DHEA: 7.48 ± 0.63, 10.59 ± 0.78; Δ5P-S: 1,652 ± 154,1,486 ± 130; DHEA-S: 2,122 ± 134, ± 134,1,906 ± 134. Umbilical artery Δ5P-S, DHEA-S, and DHEA levels were significantly higher than UV levels, whereas the reverse was true for Δ5P and 16α-OH DHEA. The inverse arterio-venous (A-V) gradient for 16α-OH DHEA was contrary to previous published reports using pooled samples. Comparison by linear regression of paired UA and UV steroid concentrations of Δ5P, Δ5P-S, DHEA, and DHEA-S revealed a significant correlation (P < 0.01) for each st...
TL;DR: The results suggest that energy obtained from succinate oxidation can be diverted from phosphorylation to support steroidogenesis.
Abstract: No differences in oxidative phosphorylation or in the per cent of [4-14C]cholesterol converted to [4-MC]pregnenolone and [4-14C]progesterone were found in ovarian mitochondria of immature rats after treatment with 20 IU of pregnant mare serum gonadotropin (PMSG) iv 30 min before killing. However, treatment of immature rats with 20 IU of PMSG SC 54 h prior to killing decreased the ADP:O ratio and increased the per cent of [4-14C]- cholesterol conversion. Electron microscopic studies showed that mitochondria with lamellar cristae were prominent in ovaries of untreated rats, while large pleomorphic mitochondria and mitochondria with tubulovesicular cristae dominated in ovaries of PMSG-treated rats. Ovarian homogenates separated by zonal centrifugation showed three peaks of cytochrome oxidase activity which shifted to the heavier end of the gradient after PMSG treatment. These studies suggest that PMSG treatment influences ovarian mitochondria, possibly by stimulating the synthesis of additional functional co...
TL;DR: The electron paramagnetic resonance (EPR) spectra of rat adrenal zona fasciculate mitochondria showed peaks corresponding to low spin ferric cytochrome P-450 with apparent g values of 2.424, 2.248 and 1.917, and weak signals due to high spin ferrics cyto chrome P- 450 with gx values of 8.08 and 7.80.