Showing papers on "Pregnenolone published in 1982"
TL;DR: The studies suggest that the effects of SCP2 are related to delivery of cholesterol from preformed stores to and into mitochondria for initiation of steroid hormone synthesis, and may represent an important modulator of sterol metabolism in adrenal cortical cells.
219 citations
TL;DR: It is suggested that glucocorticoids directly suppress Leydig cell steroidogenesis by decreasing gonadotropin stimulation of cAMP production and the activity of 17 alpha-hydroxylase.
Abstract: The mechanism whereby glucocorticoids directly inhibit gonadotropin-stimulated testosterone production was studied by using primary cultures of testicular cells from adult hypophysectomized rats. Testicular cells were maintained in serum-free media with hormone treatments administered on Day 8 and media collected 48 h later for steroid and cAMP measurement. Highly purified human chorionic gonadotropin (hCG) increased testosterone production relative to controls. Concomitant administration of either natural (cortisone greater than deoxycorticosterone = aldosterone) or synthetic (dexamethasone greater than or equal to prednisolone) corticosteroids inhibited hCG-stimulated testosterone production in a dose-dependent manner. Dexamethasone at 10(-7) M decreased testosterone production by approximately 50-60% and this inhibitory effect was reversible upon removal of the glucocorticoid. In the presence or absence of a phosphodiesterase inhibitor, dexamethasone decreased hCG-stimulated cAMP production by approximately 60%. Dexamethasone also decreased testosterone production induced by cholera toxin and (Bu)2 cAMP by 43 and 63%, respectively. The dexamethasone suppression of testosterone production was accompanied by marked decreases in androstenedione (80% decrease) and 17 alpha-hydroxyprogesterone (57%) production, with a lesser effect on progesterone production (28% decrease) and no effect on pregnenolone production. Exogenous progesterone and 17 alpha-hydroxyprogesterone augmented hCG-stimulated testosterone production. Dexamethasone reduced the conversion of exogenous progesterone to testosterone by 33% but did not affect the conversion of 17 alpha-hydroxyprogesterone to androstenedione and testosterone, suggesting a specific inhibition of 17 alpha-hydroxylase. These results suggest that glucocorticoids directly suppress Leydig cell steroidogenesis by decreasing gonadotropin stimulation of cAMP production and the activity of 17 alpha-hydroxylase.
155 citations
TL;DR: It is concluded that 25-OH-cholesterol is an effective steroidogenic substrate for rat luteal tissue and information regarding the maximal capacity of lutesal tissue to produce progestins in vitro can be obtained.
Abstract: The metabolism of 25-hydroxycholesterol 25- OH-cholesterol) to progestins by mitochondria and dispersed cells prepared from ovaries of PMSG-hCG-primed rats was studied. Mitochondria converted [3H]25-OH-cholesterol into [3H]pregnenolone and [3H]progesterone. Unlabeled 25-OH-cholesterol also stimulated mitochondrial steroidogenesis in a dosedependent, saturable fashion. A direct relationship between rates of steroid synthesis in the presence of 25-OH-cholesterol and mitochondrial cytochrome P-450 levels was found. Although steroid production and cytochrome P-450 content per milligram protein were higher in mitochondria prepared from ovaries removed on day 8 post hCG than on either day 1 or day 14, steroid production per nanomole cytochrome P-450 was similar. Treatment of rats with hCG 1 h before killing significantly increased mitochondrial steroid synthesis from endogenous substrate but had no effect on metabolism of 25-OH-cholesterol. Dispersed cells increased progestin production by 6-fold when incubated...
142 citations
TL;DR: The modulation of ovarian steroidogenesis by epidermal growth factor (EGF) was investigated in cultured rat granulosa cells and the effects of EGF were shown to be time-dependent.
136 citations
TL;DR: It is suggested that calcium ions significantly modulate LH-stimulated progesterone biosynthesis in isolated ovarian cells in vitro and at intracellular loci distal to the actual generation of cAMP.
Abstract: Incubation of swine granulosa cells in chemically defined medium selectively deficient in calcium ions markedly impaired progesterone production in response to submaximal and maximally stimulating concentrations of LH. Accumulation of progesterone in response to LH was reduced significantly in both cells and medium, without a discernible shift in the time-course of progestin production. The reduction in progesterone accumulation could not be accounted by increased formation of the catabolite 20 alpha-hydroxypregn-4-en-3-one. In addition, progesterone secretion basally or in response to exogenously supplied pregnenolone was not altered in calcium-deficient incubations. Administration of verapamil or diltiazem, organic inhibitors of net transmembrane calcium uptake, also suppressed LH-stimulated progesterone production. Conversely, micromolar concentrations of the divalent cation ionophore A23187 significantly enhanced the stimulatory effects of LH. The mechanisms of calcium action were examined further in relation to the cAMP effector system. Calcium deprivation significantly suppressed the dose-dependent accumulation of cAMP in granulosa cells treated with LH but had no effect on basal levels. Omission of calcium ions from the extracellular medium also markedly impaired production of progesterone in response to 8-bromo-cAMP, cholera toxin, or 3-isobutyl-l-methylxanthine. The present studies suggest that calcium ions significantly modulate LH-stimulated progesterone biosynthesis in isolated ovarian cells in vitro. Specific regulatory actions of calcium ions in granulosa cells may be exerted at several levels, including LH-stimulated cAMP accumulation and at intracellular loci distal to the actual generation of cAMP.
93 citations
TL;DR: Evidence is shown that 17 alpha,20 beta-diOHprog is the naturally occurring maturation-inducing steroid of amago salmon, and the role of other steroid hormones, particularly the possible involvement of corticosteroids, in the control of final oocyte maturation in teleosts is explored.
Abstract: The effect of partially purified chinook salmon gonadotropin (SG-G100) and a number of steroids on the induction of germinal vesicle breakdown (GVBD) in amago salmon (Oncorhynchus rhodurus) oocytes (with intact follicle layers) was investigated in vitro. SG-G100 was effective only at the highest concentration tested (1 microgram/ml). 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOHprog) was the most potent maturation-inducing steroid tested, followed by 17 alpha-hydroxyprogesterone. Testosterone or deoxycorticosterone (DOC) enhanced the rate of GVBD in response to SG-G100. DOC also enhanced the response to 17 alpha,20 beta-diOHprog but testosterone was without effect, suggesting that DOC has a direct action on the oocyte while testosterone probably acts at the level of the follicle. Estradiol-17 beta had no effect on GVBD in response to SG-G100 or 17 alpha,20 beta-diOHprog. The action of SG-G100 was shown to be dependent on the synthesis of a second delta 4 steroidal mediator of maturation since cyanoketone, a specific inhibitor of 3 beta-hydroxy-delta 5-steroid dehydrogenase, completely abolished the maturational effects of the gonadotropin and pregnenolone but not delta 4 steroids. Radioimmunoassay of media in which oocytes were induced to mature in vitro with SG-G100 revealed significantly elevated levels of progesterone and 17 alpha,20 beta-diOHprog. Estradiol-17 beta levels, high in control media, were only elevated twofold by SG-G100. Levels of the two progestogens were extremely low or nondetectable in media in which oocytes were incubated with cyanoketone, while estradiol-17 beta levels remained high. These results are discussed in relation to other evidence indicating that 17 alpha,20 beta-diOHprog is the naturally occurring maturation-inducing steroid of amago salmon. The role of other steroid hormones, particularly the possible involvement of corticosteroids, in the control of final oocyte maturation in teleosts is explored.
82 citations
TL;DR: A revised model of the fetoplacental steroidogenic unit is presented which may explain both normal and fetal hyperplasia and postnatal involution of the adrenal cortex and the variations from this pattern seen in apituitary children.
Abstract: The effect upon steroidogenesis of adding various steroids produced by the placenta was studied in short term cultures of human fetal adrenal cells. The addition of high concentrations (103 ng/ml) of estrone or estriol inhibited the production of cortisol, but only the former elicited a parallel increase in dehydroepiandrosterone (DHA) production. Estradiol was effective in inhibiting Δ4-3-ketosteroid production at concentrations of 10-100 ng/ml, levels which approach those found in the fetal circulation, while DHA production was increased at concentrations of 1 eg/ml. The addition of progesterone (4 eg/ml) to the medium caused increased production of cortisol and corticosterone, but had no effect on DHA production. Pregnenolone (4)eg/ml) increased the basal production of DHA and slightly impaired both basal and ACTH-stimulated aldosterone production, but had no effect on cortisol production. The data demonstrate that of the many fetal and placental factors which have been studied to date, only ACTH and e...
80 citations
TL;DR: The present results coupled with the observed GnRH stimulation of 20 alpha-HSD activity reported earlier suggest that GnRH inhibits the FSH stimulation of progesterone production by decreasing the conversion of pregnenolone to progester one as well as by increasing the metabolism of progestersone.
Abstract: The mechanism by which gonadotropin-releasing hormone (GnRH) inhibits ovarian progesterone production was investigated by studying the GnRH modulation of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD)/delta 5-delta 4-isomerase activity in cultured rat granulosa cells. Ovarian granulosa cells, obtained from immature hypophysectomized estrogen-treated rats, were incubated with various hormones in vitro, and 3 beta-HSD activity was determined by measuring the conversion of radiolabeled pregnenolone to progesterone. Treatment with FSH increased the apparent maximal velocity of the enzyme by about 6-fold in a dose-dependent manner, with an ED50 value of 3.58 ng/ml. FSH treatment also resulted in an approximately 10-fold increase in the apparent Km of this enzyme (from 0.46 to 4.98 microM). In contrast, concomitant treatment with GnRH (10(-8) M) inhibited the FSH-stimulated increase in enzyme activity by about 27%. This inhibitory effect of GnRH was associated with a decrease in the apparent maximal velocity, while the apparent Km remained unchanged. Furthermore, the inhibitory effect of GnRH was observed whether the enzyme activity was expressed per mg protein or per mg DNA. Concomitant treatment with 10(-6) M of a GnRH antagonist, [D-pGlu1,D-Phe2,D-Trp3,6]GnRH, completely blocked the inhibitory effect of GnRH. In contrast to the inhibitory effect of GnRH on FSH-stimulated 3 beta-HSD activity, treatment with GnRH alone increased enzyme activity by about 40%. This was accompanied by a slight but significant stimulation of basal progestin production by GnRH in granulosa cells. The present results coupled with the observed GnRH stimulation of 20 alpha-HSD activity reported earlier suggest that GnRH inhibits the FSH stimulation of progesterone production by decreasing the conversion of pregnenolone to progesterone as well as by increasing the metabolism of progesterone.
59 citations
TL;DR: It is concluded that human fetal membranes at term can produce progesterone and this production may be modulated by other steroids of fetal or maternal origin, and local regulation of progestersone production may have an important influence on local prostaglandin generation and hence on myometrial contractility.
Abstract: We have studied the ability of human fetal membranes (amnion, chorion, and decidua) to produce pro-gesterone. Membranes were obtained from women at 38–41 weeks pregnancy following spontaneous onset of labor. The tissues were dispersed into single cell preparations using 0.05% collagenase in a Krebs-Ringer buffer system. Progesterone was measured by specific RIA. All 3 tissues produced progesterone in a significant dose-response relationship with added pregnenolone but chorion was significantly more active than the other membranes. Equimolar concentrations of dehydroepiandrosterone, estrone or estradiol cause significant inhibition (to <50%) of this activity but dehydroepiandrosterone sulfate and estriol did not. We conclude that human fetal membranes at term can produce progesterone and this production may be modulated by other steroids of fetal or maternal origin. Local regulation of progesterone production, without significant changes in circulating levels of progesterone, may have an important influenc...
58 citations
TL;DR: It is demonstrated that GnRH also inhibits FSH-stimulated pregnenolone biosynthesis, probably at the side-chain cleavage enzyme step.
Abstract: The mechanism by which GnRH inhibits ovarian progesterone production was investigated by studying the GnRH modulation of pregnenolone biosynthesis in cultured rat granulosa cells. Granulosa cells from hypophysectomized, estrogentreated rats were incubated for 2 days with various hormones in vitro. Pregnenolone production was measured in the presence of cyanoketone, which inhibits the conversion of pregnenolone to progesterone. FSH stimulated pregnenolone production in a dose-dependent manner (ED50, 4.47 ng/ml). Concomitant treatment with GnRH resulted in a dose-dependent decrease in FSH-stimulated pregnenolone production (ID50,6.3 × 10-9 M; maximal decrease, ∼50%). In contrast, treatment with high doses of GnRH alone stimulated pregnenolone production (ED50, 2.95 × 10-8 M), reaching a maximal level of about 10% that induced by FSH. Treatment with a GnRH antagonist, [Ac-D-Phe1, D-pCl-Phe2, D-Trp3>6]GnRH, did not affect either basal or FSH-stimulated pregnenolone production, but blocked both inhibitory and ...
53 citations
TL;DR: Direct addition of possible secreted products of pregnenolone—androstenedione, progesterone, and 17-hydroxyprogesterone—was found to cause loss of 21-hydroxylase activity measured as 21-deoxycortisol conversion to cortisol.
Abstract: When primary bovine adrenocortical cells were cultured in a serum- and lipoprotein-free medium, the pattern of steroids synthesized from pregnenolone precursor was altered by prior treatment with ACTH and by prior exposure to pregnenolone. As evidenced by the high performance liquid chromatographic profile of steroids synthesized from pregnenolone, ACTH induced 17-hydroxylase activity, whereas, regardless of ACTH treatment, prior exposure to pregnenolone reduced 21-hydroxylase activity. Direct addition of possible secreted products of pregnenolone—androstenedione, progesterone, and 17-hydroxyprogesterone (17-hydroxypregn-4-ene-3,20-dione)—was found to cause loss of 21-hydroxylase activity measured as 21-deoxycortisol (llβ,17-dihydroxypregn-4-ene-3,20-dione) conversion to cortisol. Several steroids that caused loss of 11β-hydroxylase activity did not affect 21-hydroxylase. Androstenedione suppressed both 21- and llβ-hydroxylase but did not affect 17-hydroxylase or C17,20-lyase activities. The time course o...
TL;DR: Fetal and maternal plasma estrone and estrone sulfate concentrations underwent a terminal rise over the last 4 days of gestation that was a mirror image of the fall in plasma pregnanolone and pregnenolone sulfate.
Abstract: Parturition in the sheep is preceded by a complex series of changes in both fetal and maternal plasma-steroid hormone concentrations. Using the chronically catheterized fetal sheep preparation, we measured unconjugated and sulfoconjugated pregnenolone, 17α-hydroxypregnenolone, dehydroepiandrosterone, and estrone in fetal and maternal plasma over the final 20 days before spontaneous vaginal delivery at term. Where appropriate, third degree polynomial functions were fitted to the changing plasma hormone concentration profile. Fetal and maternal plasma pregnenolone and pregnenolone sulfate both fell from maximum values in the last 4 days of gestation. Fetal and maternal plasma estrone and estrone sulfate concentrations underwent a terminal rise over the last 4 days of gestation that was a mirror image of the fall in plasma pregnenolone and pregnenolone sulfate. Maternal 17α-hydroxypregnenolone rose over the last 4 days of gestation. Fetal 17α-hydroxypregnenolone, maternal and fetal plasma dehydroepiandroster...
TL;DR: The data suggest that the testicular steroidogenic pathway in rhesus monkeys retain its ability to respond to LH stimulation during treatment with the LHRH agonist while the basal testosterone levels are reduced.
Abstract: The effects of chronic administration of [D-Ser(TBU)6, des-Gly-NH2 10]LHRH ethylamide (Buserelin, Hoe 766) on plasma LH, pregnenolone, 17-hydroxyprogesterone, testosterone and dihydrotestosterone levels were studied in a nonhuman primate species, the rhesus monkey. After 1 week of daily administration of 25 micrograms of Hoe 766, the LH response measured after 3 h and 7 h is markedly inhibited when compared to the previous week's response and a slight decrease in basal LH levels is observed. A small rise of plasma LH is, however, always seen 3 h after administration of the peptide during the whole treatment period. Serum testosterone levels display a rapid stimulation from 7 to 35 ng/ml 3 h after the first administration of Buserelin and increase progressively up to at least 12 h (44 ng/ml). Plasma concentrations of 17-hydroxyprogesterone increase more slowly from 2.0 to 3.4 ng/ml during the first 3 h and reach 9.5 ng/ml 9 h later. By contrast, there are no or minimal changes or serum pregnenolone and dihydrotestosterone levels following the first injection of Hoe 766 and during the course of the study. While the acute testosterone response to Buserelin measured at 3 h is not affected in up to seven weeks of treatment with the peptide, the duration of testosterone and 17-hydroxyprogesterone response measured at later time intervals (7 h, 12 h) is decreased to 20% to 50% of control. The data suggest that the testicular steroidogenic pathway in rhesus monkeys retain its ability to respond to LH stimulation during treatment with the LHRH agonist while the basal testosterone levels are reduced. The close correlation observed between reduced serum LH and testosterone concentrations suggest that pituitary desensitization is the main factor responsible for the partial inhibition of basal testosterone concentration in rhesus monkeys.
TL;DR: The studies presented herein were undertaken to discern if modifications of the steroidogenic pathway occur during ovine fetal adrenal development.
Abstract: The studies presented herein were undertaken to discern if modifications of the steroidogenic pathway occur during ovine fetal adrenal development. Isolated adrenal cells from 120-day-old fetuses (controls), 120-day-old fetuses which were perfused for 5 days with ACTH (ACTH-treated), and newborn lambs were incubated. with 14C-labeled pregnenolone [3β-hydroxy-5-pregnen-20-one (P5)]. The time courses (30, 60, 90, and 120 min) of P5 disappearance and the formation of labeled progesterone, 11-deoxycorticosterone (21-hydroxy-4-pregnene-3,20-dione), corticosterone, 17α-hydroxypregnenolone (3β,17α-dihydroxy-5-pregnene-20-one), 17α-dihydroxyprogesterone (17α-hydroxy-4-pregnene-3-one), 11-deoxycortisol (17α,21-dihydroxy-4-pregnene-3,20-dione), and cortisol were measured. The rate of P5, disappearance from the medium was much slower in control fetuses than in ACTH-treated fetuses or newborn lambs. In control fetuses, after 2 h, only 45% of P5 had disappeared, of which more than 85% was metabolized through the 17-de...
TL;DR: The present studies demonstrate that estradiol and LH significantly stimulate progesterone production, at least in part, by augmenting pregnenolone biosynthesis, but not by inhibiting progester one catabolism.
Abstract: Well differentiated swine granulosa cells in monolayer culture were employed to investigate the mechanisms by which estradiol amplifies the stimulatory actions of LH in the later stages of follicular maturation. The facilitative interaction between estradiol and LH could not be attributed to altered rates of catabolism of progesterone to 20α-hydroxypregn- 4-en-3-one. Moreover, estradiol, LH, and estradiol combined with LH clearly stimulated pregnenolone production, measured in the presence of trilostane, to inhibit 3β-hydroxysteroid dehydrogenase- Δ5-4isomerase activity. Thus, at least one component of the synergism between estradiol and LH must reside at or proximal to the cholesterol side-chain cleavage system. In the absence of lipoproteins, the magnitude of the synergism between estradiol and LH was significantly reduced. However, the facilitative interaction between estradiol and LH could still be observed in lipoprotein-deficient and serum-free medium and after the administration of ML-236B to suppr...
TL;DR: The results indicate that hyperglycemia induced by streptozotocin is not inconsistent with production of an LH surge or with ovulation following ovarian stimulation by PMS, but the lowered production of progesterone appears to be a primary factor in the reduced ovulatory rate.
Abstract: Immature female rats were injected with streptozotocin (60 mg/kg, iv) 3 to 4 days prior to the injection (iv) of 20 IU of pregnant mare's serum gonadotropin (PMS). Animals were killed at various intervals and the serum levels of estradiol, luteinizing hormone (LH), and progesterone were determined by radioimmunoassays. The ovarian steroid 17α-hydroxylase activity was determined by a tritium exchange assay using pregnenolone as the substrate. Ovulation was determined 72 hr after PMS by flushing of the oviducts. The diabetes mellitus induced by the drug reduced the number of animals ovulating and in some animals the number of ova shed when compared to controls. However, a surge in LH, which reached a peak at 60 hr, was seen in the diabetic animals; a larger peak with the same timing was found in the controls. Changes in ovarian 17α-hydroxylase also indicated that an increase in LH release occurred in the diabetic animals at about 60 hr. Estradiol levels were higher, but progesterone levels lower, in...
TL;DR: A perifusion technique for cells attached to plastic was developed and was applied to the kinetics of LH action on steroidogenesis in tumour and immature Leydig cells, and it was concluded that LeYDig cells attachedto plastic can be used for investigation of acute actions of LH on steroidsogenesis.
Abstract: Tumour Leydig cells and normal mature Leydig cells lost their steroidogenic response (pregnenolone and testosterone secretion) to LH after 24 h of culture Immature cells showed a 2-fold increase in the basal pregnenolone secretion and no change in the LH-dependent pregnenolone secretion after 24 h of culture, whereas the LH-dependent steroidogenesis decreased after 48 h None of the 3 cell preparations showed morphological signs of degeneration during a culture period of more than 7 days Histochemical 3 beta-hydroxysteroid dehydrogenase activity in isolated immature Leydig cells disappeared during the first 2 days of the culture period and re-appeared after 5--7 days Testosterone production by mature Leydig cells decreased during the first hours after exposure to LH, whereas pregnenolone secretion remained constant From these results it was concluded that Leydig cells attached to plastic can be used for investigation of acute actions of LH on steroidogenesis A perifusion technique for cells attached to plastic was developed and was applied to the kinetics of LH action on steroidogenesis in tumour and immature Leydig cells The first stimulation of pregnenolone secretion occurred within 5 min, but a full stimulation was only obtained after 20--30 min This was followed by a gradual decrease in the stimulated steroid secretion to approximately 50% after 60 min
TL;DR: A sensitive cell-free assay was developed for the analysis of corticotropin-dependent factors that stimulate the rate-limiting step of adrenal steroidogenesis and prevented the production of these steroidogenic factors in vivo upon stimulation but had no effect in vitro, suggesting a post-translational cascade involved in the activation of the cholesterol side-chain split.
Abstract: A sensitive cell-free assay was developed for the analysis of corticotropin-dependent factors that stimulate the rate-limiting step of adrenal steroidogenesis. In this assay adrenal post-mitochondrial supernates from corticotropin-stimulated rats caused a 10- to 100-fold increase in the de novo synthesis of pregnenolone and progesterone. A similar stimulation was observed by corresponding fractions from Leydig cells and mouse Y-1 adrenal tumor cells, but not from rat liver. Subcellular fractionation of rat adrenal tissue showed several steroidogenic factors to be present in various compartments. Recombination of them produced highly synergistic effects. The activation of some components could also be demonstrated in vitro, suggesting a cascade of events possibly linking the cAMP-dependent phosphorylation pathway with the rate-limiting step. Cycloheximide prevented the production of these steroidogenic factors in vivo upon stimulation but had no effect in vitro, suggesting a post-translational cascade involved in the activation of the cholesterol side-chain split.
TL;DR: It appears that the inhibitory action of cannabinoids is exerted beyond LH binding and activation of adenylate cyclase and prior to pregnenolone formation in the gonadal steroidogenic pathway.
Abstract: delta 1-Tetrahydrocannabinol (delta 1-TCH), the major psychoactive constituent of marihuana, was found to suppress the preovulatory surge of gonadotropins and thereby to prevent ovulation in rats, rabbits and rhesus monkeys. These studies suggested that the drug acts primarily on the hypothalamus to suppress luteinizing hormone releasing hormone (LHRH) secretion. The aim of the present study was to examine the direct effect of delta 1-THC, the psychoactive constituent of marihuana and cannabidiol (CBD), one of its nonpsychoactive constituents, on preovulatory rat follicles in vitro. Both cannabinoids inhibited follicular steroidogenesis in a dose-dependent manner. Basal accumulation of progesterone (P), testosterone (T) and estradiol-17 beta (E2) was reduced up to 60% by the highest doses examined (100-200 microM). The luteinizing hormone (LH)-stimulated increase in P and T was inhibited by 75-88% by the highest doses of both cannabinoids (50-200 microM), while E2, accumulation was inhibited by only 40%. It appears that the inhibitory action of cannabinoids is exerted beyond LH binding and activation of adenylate cyclase and prior to pregnenolone formation in the gonadal steroidogenic pathway. In addition to this anti-steroidogenic effect, both cannabinoids induced resumption of meiosis in follicle-enclosed oocytes cultured in hormone-free medium; 200 microM delta 1-THC resulted in 80% maturation and CBD in 75%. It seems that the action of cannabinoids on rat follicles in vitro is unrelated to their psychotropic activity.
TL;DR: It is interpreted to mean that TMB-8 blocks the steroidogenic effect of dibutyryl cyclic AMP by interfering with the mobilization of a cellular pool of calcium that is probably localized to the endoplasmic reticulum.
TL;DR: It is concluded that the high levels of delta 5P sulfate and D sulfate found in human fetal plasma arise not only as a consequence of the high capacity of the human fetal adrenal fetal zone to sulfurylate the unconjugated compounds, but also as a result of the conversion of cholesteryl sulfate to delta5P sulfates and thence to D sulfates.
Abstract: The sulfurylation of pregnenolone (Δ5P), dehydroepiandrosterone (D) and cholesterol in subcellular fractions of the separated zones of normal human fetal adrenals as well as the mitochondrial sterol desmolase activities are investigated. The values obtained are compared to those found in adrenal tissues of anencephalics and adults. The β8-hydroxysteroid sulfotransferase activity is localized principally in the cytosolic fraction of the tissues assayed. The highest rate of sulfurylation of Δ5P and D is found in the cytosol of the fetal zone (5 nmol min-1 mg protein-1). The corresponding activities in fetal neocortex, anencephalic, and adult adrenocortical tissues are one tenth of that in the fetal zone. Cholesterol sulfurylation is not detectable under similar assay conditions. The specific activities of cholesterol and cholesteryl sulfate desmolases are 3- 4-fold greater in the fetal zone than in the neocortex. Cholesterol desmolase activity, but not cholesteryl sulfate desmolase activity, is found in adr...
Journal Article•
TL;DR: The data supports a general inhibitory effect of high ascorbic acid on the steroid hydroxylations, and a possible regulatory role of ascorBic Acid on the conversion of pregnenolone to delta 4 and delta 5 steroids.
Abstract: Guinea pig ovarian whole tissue homogenates were incubated with [14C]-labelled cholesterol, pregnenolone, and progesterone. Testicular homogenates were incubated with [14C]-progesterone. All incubations were carried out in the presence of 0, 0.5, 1.0, or 2.0 mM ascorbic acid. The conversion of cholesterol to pregnenolone was significantly decreased in testosterone and progesterone production. The addition of 0.5 mM ascorbic acid increased the conversion of pregnenolone to delta 4 steroids and decreased its conversion to delta 5 steroids, relative to the other ascorbic acid treatments. The conversion of progesterone to 17 A-hydroxyprogesterone was significantly decreased in the presence of 1.5 mM ascorbic acid over the O mM treatment. The data supports a general inhibitory effect of high ascorbic acid on the steroid hydroxylations, and a possible regulatory role of ascorbic acid on the conversion of pregnenolone to delta 4 and delta 5 steroids.
TL;DR: In this paper, it was shown that in the absence of added pregnenolone, NAD+ was not effective in preventing ethanol's effects, but only when labeled or unlabeled pregnenoline was added.
TL;DR: The tumour was cultured in vitro and shown by high performance liquid chromatography to produce predominantly DOC from tritiated pregnenolone, with no detectable aldosterone, in agreement with the in vivo results.
Abstract: SUMMARY
A 51-year-old female was thought to have Conn's syndrome because she had hypertension, hypokalaemia and low plasma renin activity. The cause was not aldosterone excess, but there was an adrenal cortical carcinoma producing 11-deoxycorticosterone (DOC) in extremely large quantities, with ineffective 1 l/?-steroid hydroxylation. Plasma and urinary aldosterone levels were within the normal range. Blood levels of other steroids including those on the pathways of formation of glucocorticoids and sex steroids were unaffected. The tumour was cultured in vitro and shown by high performance liquid chromatography (HPLC) to produce predominantly DOC from tritiated pregnenolone, with no detectable aldosterone, in agreement with the in vivo results.
TL;DR: The results demonstrate that the augmenting effect of androgens upon FSH-stimulated progesterone biosynthesis is not due to changes in the conversion of progestersone to 20 alpha-OH-P, but involves an enhancing action upon 3 beta-HSD/delta 5,delta 4-isomerase complexes and additional enzymes prior to pregnenolones biosynthesis.
TL;DR: The binding data are indicative of cooperative binding of three ligands (H+, cholesterol, and adrenodoxin) to cytochrome P-450scc, and pregnenolone binds competitively with cholesterol while reverting the spin state to a low spin complex.
TL;DR: Yields of an unidentified polar metabolite increased with temperature and it is suggested that this may play a regulatory role in elasmobranch reproduction.
Abstract: 1. 1. Testes of the dogfish, Scyliorhinus caniculus , were incubated with [ 3 H]pregnenolone and [ 3 H]testosterone at a range of temperatures from 1 to 36°C. 2. 2. Yields of testosterone from pregnenolone were maximal between 11 and 16°C, corresponding to the breeding temperature of the species. 3. 3. Yields of glucuronides and sulphates increased from 1 to 26°C. 4. 4. Yields of an unidentified polar metabolite increased with temperature and it is suggested that this may play a regulatory role in elasmobranch reproduction.
TL;DR: The results directly demonstrate that the human testis is able to respond rapidly to hCG stimulation, and the first effect of hCG might be general facilitation of C21 and C19 steroid release to the circulation.
TL;DR: The molecular mass, the subcellular localization and the sensitivity to phosphorylation in the presence of inhibitors of protein synthesis indicate that the 33 000-Da protein could be similar to ribosomal protein S6.
Abstract: Addition of lutropin (luteinizing hormone, 'LH') and 3-isobutyl-1-methylxanthine to tumour Leydig cells stimulated phosphorylation of five proteins, of 17 000, 22 000, 24 000, 33 000 and 57 000 Da. Phosphorylation of these proteins coincided with increased pregnenolone production. Phosphorylation of a 33 000-Da protein was lutropin-dependent in Leydig cells isolated from a Leydig-cell tumour, from immature testes or from mature testes. In tumour Leydig cells this protein was present in the small ribosomal subunit. Incubation of tumour Leydig cells with either cycloheximide or puromycin inhibited both basal and lutropin-dependent pregnenolone production, by approx. 90% and 98% respectively. In contrast, basal pregnenolone production in Leydig cells from immature and mature testes was insensitive to cycloheximide or puromycin. Cycloheximide or puromycin increased phosphorylation of the 33 000-Da phosphoprotein by approx. 130% and 80% respectively (effect of lutropin/3-isobutyl-1-methylxanthine on phosphorylation: 100%). The molecular mass, the subcellular localization and the sensitivity to phosphorylation in the presence of inhibitors of protein synthesis indicate that the 33 000-Da protein could be similar to ribosomal protein S6.