Showing papers on "Pregnenolone published in 1977"
TL;DR: The low, but significant testicular secretion of both 5alpha-hydrotestosterone and androsterone suggests that these two steroids are testicular androgen metabolites, and that androgen metabolism in this tissue may be monitored by way of their measurement in spermatic vein blood.
Abstract: Seven unconjugated neutral steroids, including testosterone and some of its precursors and metabolites, were measured in the peripheral and spermatic venous blood of males, employing specific radioimmunoassays after the fractionation of steroids on Lipidex-5000® (hydroxyalkoxypropyl Sephadex) microcolumns. Respective mean concentrations (ng/ml) and ranges of steroids estimated in peripheral and spermatic venous blood in all groups of patients were as follows: pregnenolone, 0.71 (0.29–2.39) and 10.97 (0.83–30.1); progesterone, 0.31 (0.02–0.57) and 10.17 (1.51–33.24); 17α-hydroxyprogesterone, 1.04 (0.48–2.20) and 37.33 (1.68–141.00); androstenedione, 1.01 (0.26–2.65) and 11.87 (0.97–30.18); testosterone, 3.84 (0.63–10.64) and 255.1 (2.85–619.1); 5α-dihydrotestosterone, 0.19 (0.07–0.28) and 3.74 (0.04–9.71); androsterone, 0.27 (0.12–0.47) and 0.97 (0.20–2.15). Concentrations are similar to those estimated by mass spectrometry and protein binding assays, except for androsterone which has not previously been m...
133 citations
TL;DR: It is suggested that for the early detection of the LH surge and prediction of the subsequent ovulation daily assays of plasma progesterone are of more value than the assay of the other steroids investigated.
Abstract: In an attempt to analyze the multiple changes and interactions in circulating steroid levels in the peri-ovulatory and peri-menstrual periods, the plasma levels of immunoreactive luteinizing hormone (LH), progesterone and unconjugated pregnenolone, dehydroepiandrosterone, testosterone, oestradiol and oestrone were assayed daily during a complete cycle in 17 normally menstruating women. In 14 of the 17 subjects studied androstenedione and unconjugated dihydrotestosterone were also estimated. The day of the LH-peak and the first day of menstruation, respectively, were used to synchronize the peri-ovulatory and peri-menstrual plasma levels of the various steroids. With the exception of dehydroepiandrosterone and dihydrotestosterone, the plasma levels of all steroids exhibited significant, but different changes during the cycle. Testosterone levels showed a slight but significant increase around the LH-peak, whereas the levels of pregnenolone and androstenedione were higher in the post-ovulatory than in the pre-ovulation periods. The levels of oestradiol and oestrone, as well as the ratios of oestradiol to oestrone gradually increased from the low values observed in the early proliferative phase to pre-ovulatory peak values. The relationship between peaks of oestradiol and oestrone and that of LH exhibited great individual variation. The same was true for the individual oestradiol to oestrone ratios. The combination of several steroidal signals did not improve the predictive value of the analyses. However, an increase of individual progesterone values by at least 0.35 ng/ml from the day preceding the LH-peak to the day of the LH-peak was observed in 13 of the 17 subjects. It is suggested that for the early detection of the LH surge and prediction of the subsequent ovulation daily assays of plasma progesterone are of more value than the assay of the other steroids investigated.
129 citations
TL;DR: Serum pregnenolone, progesterone, 17-hydroxyprogesterone, testosterone and 5α-dihydrotestosterone concentrations were measured radio-immunologically from a group of 200 normal girls 7–17 years of age to study the effects of bone age, breast and pubic hair developmental stages, and gynecological age on steroids.
Abstract: Serum pregnenolone, progesterone, 17-hydroxyprogesterone, testosterone and 5α-dihydrotestosterone concentrations were measured radio-immunologically from a group of 200 normal girls 7–17 years of age. Samples from postmenarcheal girls were taken on days 6–9 and 20–23 of the menstrual cycle. Steroid concentrations were related to bone age, breast and pubic hair developmental stages, and gynecological age. When the premenarcheal values and the values from postmenarcheal samples taken on days 6–9 were related to bone age, the concentrations of all the five steroids increased with advancing age. The first steroid to exhibit a significant rise was pregnenolone. This rise was first seen between the bone age groups 7.5 and 8.5 years. Testosterone was quite unchanged until 9.5 years of bone age, after which a steep increase took place until 12.5 years, the concentrations reached being 3.5-fold the initial level. Following menarche, which took place at 13.4 years of bone age in this series, a plateau was visible i...
109 citations
TL;DR: Findings indicate that cytochalasin acts after cholesterol has entered the cells and before it is subjected to side-chain cleavage in mitochondria, and that at least one effect of ACTH (and cyclic AMP) is exerted upon this transport process.
Abstract: The ability of cytochalasin B to inhibit the steroidogenic response of mouse adrenal tumor cells (Y-1) to adrenocorticotropin (ACTH) was examined with two aims: to consider the specificity of the inhibitor and to determine at what point(s) in the steroidogenic pathway it acts. Cytochalasin B did not inhibit protein synthesis or transport of [3H]-cholesterol into the cells nor did it alter total cell concentration of ATP. Together with previous evidence, this suggests that the effects of cytochalasin observed are relatively specific in these cells. Cytochalasin inhibits the increase in conversion of [3H]cholesterol to 20alpha-[3H]dihydroprogesterone (20alpha-hydroxypregn-4-en-3-one: a major product of the steroid pathway in Y-1 cells) produced by ACTH but does not inhibit conversion of cholesterol to pregnenolone by mitochondrial and purified enzyme preparations from Y-1 cells and bovine adrenal, respectively. Cytochalasin does not inhibit the conversion of pregnenolone to 20alpha-dihydroprogesterone but was shown to inhibit increased transport of [3H]cholesterol to mitochondria resulting from the action of ACTH. These findings indicate that cytochalasin acts after cholesterol has entered the cells and before it is subjected to side-chain cleavage in mitochondria. In view of the known action of cytochalasin on microfilaments, it is proposed that these organelles are necessary for the transport of cholesterol to the mitochondrial cleavage enzyme and that at least one effect of ACTH (and cyclic AMP) is exerted upon this transport process. The specificity of the effects of cytochalasin is considered in relation to this conclusion.
103 citations
TL;DR: Quantitative analysis indicated that the three forms of pregnenolone are present in bovine adrenal cortical tissue in the following amounts (mug/kg): lipoidal derivative; free steroid, 435; and sulfate, 65.
Abstract: Bovine adrenal cortical tissue contains a lipoidal derivative of pregnenolone (3beta-hydroxy-pregn-5-en-20-one) from which the free steroid can be liberated by treatment with alkali. Evidence for the presence of such an entity comes from examination of a nonpolar extract of tissue from which pregnenolone and its sulfate had been removed by chromatography. Treatment of the nonpolar fraction with alkali followed by exhaustive chromatographic analysis led to the detection of pregnenolone. The steroid was identified by both gas chromatography/mass spectrometry and double isotope procedures. Quantitative analysis indicated that the three forms of pregnenolone are present in bovine adrenal cortical tissue in the following amounts (mug/kg): lipoidal derivative, 290; free steroid, 435; and sulfate, 65. Because the only known metabolic function of pregnenolone is to serve as a precursor of the steroid hormones, these findings have far-reaching implications for steroid hormone biochemistry.
68 citations
TL;DR: The results indicate that there is a cholesterol SCC enzyme deficiency in adrenal mitochondria in this disease, and this disease is associated with congenital lipoid adrenal hyperplasia.
67 citations
TL;DR: Finds, together, the two procedures offer a sensitive, specific, and accurate means of screening inhibitors of the cholesterol side chain cleavage system.
Abstract: Absorbance changes in the spectrum of cytochrome P-450 were related to the inhibition of [26-14C]cholesterol oxidation to [14C]isocaproate and pregnenolone in mitochondria from bovine corpus luteum produced by two types of ligands. Nitrogenous inhibitors, such as aminoglutethimide, elicit an absorption maximum at about 427 nm and a minimum at about 393 nm (type II), while steroidal inhibitors, such as (20R)-20-(p-tolyl)-5-pregnene-3beta,20-diol (20-tolyl-pregnenediol), cause difference spectra with maximum at about 420 nm and minimum at about 390 nm (reverse type I). The magnitude of spectral change and the amount of inhibition of pregnenolone synthesis by aminoglutethimide are closely correlated at concentrations ranging from 5 to 750 muM and by the model steroid, 20-tolyl-pregnenediol, at concentrations from 0.5 to 25 muM. The responses are concentration dependent and linear over the range of effective concentrations. The concentrations of inhibitors for the half-maximal inhibition of pregnenolone biosynthesis are identical with the concentrations producing half-maximal spectral changes within experimental error. Displacement of substrate from cytochrome P-450 and/or stabilization of the redox potential subsequent to to the ligation of heme iron is proposed as the specific mechanism of cholesterol side chain cleavage inhibition. Finding, together, the two procedures offer a sensitive, specific, and accurate means of screening inhibitors of the cholesterol side chain cleavage system.
42 citations
TL;DR: Under similar conditions, but in the presence of a cytochrome P 450 solubilized from rat liver mitochondria, cholesterol was transformed into a more polar compound tentatively identified as 26-hydroxycholesterol.
41 citations
TL;DR: Radioimmunoassay techniques indicate the presence of testosterone in the plasma of the cuttlefish but the absence of estrogens.
37 citations
TL;DR: Sulfatase activity on [3H]dehydroisoandrosterone sulfate was inhibited by a variety of steroid sulfates, and the enzymatic activity was unchanged by freezing and thawing.
Abstract: The human fetal membranes appear to play an important role in transport and metabolism of steroids, in the maintenance of pregnancy and perhaps in the metabolic processes leading to the initiation of parturition. Therefore, steroid sulfatase activity of human fetal membranes was studied and found to reside in the chorion laeve, with the amnion totally devoid of this activity. Within the chorion laeve, the highest specific activity of sulfatase was found in a subcellular fraction rich in microsomes. Dehydroisoandrosterone sulfate and pregnenolone sulfate had similar affinities for the sulfatase enzyme with a Km of 6 μM and 4 μM, respectively. Using [3H]dehydroisoandrosterone sulfate as the substrate and chorion laeve microsomes, the pH optimum was 7.0 and the apparent temperature optimum was 53 C. Sulfatase activity on [3H]dehydroisoandrosterone sulfate was inhibited by a variety of steroid sulfates, and the enzymatic activity was unchanged by freezing and thawing. After incubation of minces of chorion lae...
36 citations
TL;DR: Elevated plasma 17-OH-pregnenolone levels in patients with Cushing's syndrome indicate adrenal carcinoma, although a normal value does not exclude this diagnosis, and ACTH has a chronic influence on the intraadrenal utilization of delta5- pregnenes in addition to stimulating their formation.
Abstract: Plasma levels of the delta5-pregnenes, pregenolone and 17-OH-pregnenolone, were measured in patients with disordered steroidogenesis. While 17-OH-pregnenolone was within the normal range in patients with hypercortisolemia due to Cushing's disease, ectopic ACTH or adrenal adenrenal adenoma, 4 of 6 patients with an adrenal carcinoma had elevated levels of this precursor. Thus, elevated plasma 17-OH-pregnenolone levels in patients with Cushing's syndrome indicate adrenal carcinoma, although a normal value does not exclude this diagnosis. Abnormal resistance of delta5-pregnenes to suppression with dexamethasone proved useful in detecting the presence of residual tumor in the post-operative evaluation of adrenal carcinoma. Basal plasma pregnenolone was within the normal range in 19 of 20 patients with Cushing's disease and was invariably normal in patients with other varieties of hypercortisolism. Since acute administration of ACTH causes marked elevation of delta5-pregnene levels while patients with chronic ACTH excess (Cushing's disease and ectopic ACTH production) have normal levels, it is suggested that ACTH has a chronic influence on the intraadrenal utilization of delta5-pregnenes in addition to stimulating their formation. In pre-menopausal women with idiopathic hirsutism, basal levels of both delta5-pregnenes were elevated (P less than 0.001). Following dexamethasone administration the absolute decrease in delta5-pregnenes levels was greater than that seen in normal subjects. This observation indicates that the metabolism of delta5-pregnenes is abnormal in patients with idiopathic hirsutism.
TL;DR: In this article, the four stereoisomers of 20, 22-dihydroxycholesterol 9, 10, 17 and 19 were synthesized from pregnenolone using a Grignard reaction on the [20S]-20-formyl-carbinol.
Abstract: The four stereoisomers of 20, 22-dihydroxycholesterol 9, 10, 17 and 19 were synthesized from pregnenolone. Vinylation of the 3, 5-cyclo derivative 1 of pregnenolone gave the [20S]-carbinol 2, which was then oxidized with m-chloroperbenzoic acid to afford the [22S]-22, 23-epoxide 3 and its [22R]-isomer 4 (7 : 2). Reaction of 3 and 4 with i-Bu2CuLi followed by acid treatment yielded 20R, 22S-dihydroxycholesterol 9 and its 20R, 22R-isomer 10, respectively. The latter triol 10 was more effectively prepared by a Grignard reaction on the [20S]-20-formyl-carbinol 14, which was derived from pregnenolone THP ether 12, through the 1, 3-dithiane derivative 13. Oxidation of 20-dehydrocholesterol acetate 16 with OsO4 gave stereoselectively the 20S, 22S-glycol 17 (R=Ac). Treatment 17 (R=Ac) with N-chlorosuccinimide-dimethylsulfide followed by reduction with LiAlH4 afforded 20S, 22R-dihydroxycholesterol 19 together with the 20S, 22S-isomer 17 (R=H) (3 : 2). Acid-catalyzed epoxide opening reactions of 20, 22-epoxycholesterols were also discussed.
TL;DR: Serum contained pregnenolone-binding activity which was distinguishable from the adrenal cytosol factor by a variet of physicochemical means and the physiological importance of this finding remains to be determined.
TL;DR: Production of sulfated 3β-hydroxy-5-ene steroids was found to be quantitatively the dominating steroidogenic function of the fetal adrenal in vivo and in incubations, and hCG stimulated endogenous biosynthesis of testosterone.
TL;DR: S steroid-induced hypertrophied placentae in rats do not participate in a compensatory mechanism for steroid hormone production toward pregnancy maintenance, and the giant placentage failed to respond to hCG.
Abstract: Placental hypertrophy was induced in pregnant rats by daily treatment with estrone (0.5 fig) and progesterone (4 mg) from day 3 through 19 combined with ovariectomy on day 12 of pregnancy. The ratio of basal zone to whole placenta was 47% by weight in these enlarged placentae on day 20 of pregnancy but only 34% in normal placentae. In each case, the basal zone tissue was homogenized and the 10,000 × g supernatant fraction was used for in vitro incubation with [7α-3H]pregnenolone as the added substrate. The normal placental tissue synthesized more progesterone and testosterone but less androstenedione and 5α-pregnane-3,20-dione than the giant placentae. Utilization of the pregnenolone substrate by the giant placentae was subnormal. Addition of 200 IU of human chorionic gonadotropin (hCG) in vitro to normal basal zone placentae sharply increased the production of progesterone, 17α-hydroxyprogesterone, androstenedione and 5α-pregnane-3,20-dione. The giant placentae failed to respond to hCG. Thus, steroid-ind...
TL;DR: Mitochondrial preparations from granulosa and theca of large follicles of porcine ovaries converted 2–3 times more [4–14C]cholesterol to [3H]pregnenolone than did mitochondria from tissues of medium (3–6 mm) follicles, while luteal mitochondria synthesized 7.1 nmol/min/mg protein.
Abstract: Mitochondrial preparations from granulosa and theca of large (7–12 mm) follicles of porcine ovaries converted 2–3 times more [4–14C]cholesterol to [4–14C]pregnenolone than did mitochondria from tissues of medium (3–6 mm) follicles. However, only small amounts of [4–14C]-progesterone were formed by mitochondria of medium and large follicles. In contrast, mitochondria of corpora lutea converted 4–5 times more [4–I4C]cholesterol to [4–14C]progesterone than did follicular mitochondria. Using [3H]pregnenolone as substrate with no exogenous NAD+, follicular mitochondria synthesized less than 1 nmol progesterone/min/mg protein while luteal mitochondria synthesized 7.1 nmol/min/mg protein. As shown by electron microscopy, luteal mitochondria resolved further by isopycnic zonal centrifugation contained almost no contamination. While 17-OH progesterone synthesis was observed in luteal mitochondria prepared by differential centrifugation, none was detected in preparations resolved further by zonal centrifugation. Ho...
TL;DR: Denervation during early pregnancy did not affect 3β-HSD activity in the interstitial gland (IG) and corpus luteum (CL), however, denervation resulted in decreased activity, interpreted as a decreased capacity of denervated ovaries to synthesize progesterone at this time in pregnancy.
Abstract: The effect of denervation on △5-3β-hydroxysteroid dehydrogenase (3β-HSD) activity with pregnenolone as substrate was studied during pregnancy. The enzyme activity, that is interpreted as the capacity to secrete progesterone, was studied in both control and experimental pregnant rats. The ovaries of experimental rats were denervated 96 h prior to sacrifice. Denervation during early pregnancy did not affect 3β-HSD activity in the interstitial gland (IG) and corpus luteum (CL). However, denervation resulted in decreased activity in both the IG and CL on days 10, 14 and 18. This reduced activity is interpreted as a decreased capacity of denervated ovaries to synthesize progesterone at this time in pregnancy.
TL;DR: Results suggest that �5-isomerase-3�3-hydroxysteroid dehydrogenase and 1 713-Hydroxysteroids dehydrogen enzyme are active in the fetal testes; in contrast, the activity of steroid sulfatase was relatively low.
Abstract: Rt fetal testes in the latter part of gestation (Days 17-21) have enzyme systems for the de novo synthesis of androgen. Under the conditions of these in vitro experiments the major androgen produced was testosterone, with lesser amounts of androstenedione and 5n-dihydrotestosterone. As little as 10 m IU of hCG added in vitro significantly increased androgen synthesis in the fetal testis on Day 19. Bovine, ovine or human LH but not bovine or ovine FSH also stimulated the synthesis of androgens by the rat fetal testis. The synthesis of testosterone was increased by the addition of precursors: 15-fold by the addition of pregnenolone, 20-fold by progesterone, and 47-fold by dehydroepiandrosterone. However, the increase was marginal in the presence of sulfates of pregnenolone or dehydroepi- androsterone. These results suggest that �5-isomerase-3�3-hydroxysteroid dehydrogenase and 1 713-hydroxysteroid dehydrogenase are active in the fetal testes; in contrast, the activity of steroid sulfatase was relatively low.
TL;DR: Radioimmunoassays for the measurement of pregnenolone, 17alpha-hydroxyprogesterone, androstenedione, dehydroepiandrosterone (DHEA) and and Frostenediol have been developed and the reliability criteria of these methods have been established.
Abstract: Radioimmunoassays for the measurement of pregnenolone, 17alpha-hydroxyprogesterone, androstenedione, dehydroepiandrosterone (DHEA) and androstenediol (5-androstene-3beta, 17beta-diol) have been developed. In addition the reliability criteria of these methods have been established. Age dependence of testosterone precursors in plasma was studied in 80 normal males aged 19 to 93 years. When a young to middle aged group (19-54 years) was compared with an old age group (67-93 years) a highly significant (P less than 0.001) decrease was observed for all the precursors studied: DHEA -68.1%, pregnenolone -60.3%, androstenediol -53.8%, 17alpha-hydroxyprogesterone -47.5% and androstenedione -39.2%.
TL;DR: The effects of ACTH in vivo on the activity of the cytosol cholesterol is investigated and whether the adrenal cortex would respond to ACTH by activation of a triglyceride lipase is investigated.
TL;DR: There was a significant (P < 0.001) difference between the levels of pregnenolone sulphate seen on the day of the LH peak and those found on the 8th day after the LHpeak, which indicated the need to investigate further the cause of this difference.
TL;DR: The data suggest that cannabinoids inhibit corticosteroidogenesis at a site between the synthesis of cAMP and of pregnenolone in Y-1 functional mouse adrenal tumor cells.
Abstract: ACTH, cholera toxin, cyclic AMP but not pregnenolone-induced steroidogenesis in Y-1 functional mouse adrenal tumor cells was significantly inhibited by delta-9-tetrahydrocannabinol, cannabidiol, and cannabinol. The inhibition of steroidogenesis could not be correlated with a general depression in cell function or viability. The data suggest that cannabinoids inhibit corticosteroidogenesis at a site between the synthesis of cAMP and of pregnenolone.
TL;DR: A practical mass fragmentographic procedure is described which is suited to in vitro studies of gonadal endocrine function and which allows reliable determination of nanogram amounts of a wide range of steroids, including those formed from deuterium-labelled precursors.
TL;DR: The enzyme system, "andien-betha synthetase", involved in the conversion of pregnenolone to 5,16-androstadien-3 beta-ol, was found mainly in the agranular microsomes but had a lower specific activity than those of the two enzymes of androgen biosynthesis that have been studied.
TL;DR: Testes from monkeys and humans of different ages converted significant amounts (up to 70%) of progesterone and pregnenolone to 17α-hydroxyprogesterone, androstenedione, testosterone, 20 α-hydroxypregn- 4-en-3-one and/or 16α-HydroxyproGESterone.
Abstract: Testicular homogenates from rhesus monkeys 1.0, 2.0, 2.5, 2.7, 2.8, 3.0, 7, 8, 8.5 and 9 years of age and those from 33- and 100-day-old rats were incubated with 3H-progesterone, 3H-testosterone and 14C-pregnenolone in the presence of co-factors. In addition, homogenates of testes obtained from patients 3, 4, 5, 7, 15 and 83 years of age at the time of orehiectomy were incubated with 3H-progesterone and 14C-pregnenolone. After incubation, radioactive products were separated and identified by column and paper chromatography with derivative formation and recrystallization to constant specific activity. Testes from monkeys and humans of different ages converted significant amounts (up to 70%) of progesterone and pregnenolone to 17α-hydroxyprogesterone, androstenedione, testosterone, 20α-hydroxypregn- 4-en-3-one and/or 16α-hydroxyprogesterone. Testes of monkeys 1.0–9 years of age converted 1–30% of testosterone to androstenedione. However, no or very small amounts (less than 0.4% of each product) of 5α-reduce...
TL;DR: It is suggested that preimplantation mouse embryo does not possess enzyme activities for steroid metabolism, as incubated with radioactive pregnenolone, progesterone or dehydroepiandrosterone for various periods of time.
Abstract: Mouse preimplantation embryos were incubated with radioactive pregnenolone, progesterone or dehydroepiandrosterone for various periods of time. These substrates were not converted to metabolites even after incubation of 120 h. We suggest that preimplantation mouse embryo does not possess enzyme activities for steroid metabolism.
TL;DR: The findings indicate that the critical role of calcium in the steroidogenic process is associated with early events in the interaction of ACTH with the cell membrane; one of the early events includes activation of PG synthesis through a mechanism involving enzyme activation rather than de novo synthesis of new enzyme protein.
TL;DR: The spongy zone (SZ) syncytiotrophoblast has been identified as the prinicipal site of progesterone synthesis in the placenta of the guinea-pig and the results suggested that the yolk sac was able to synthesize progester one and metabolize steroids in vitro.
Abstract: The spongy zone (SZ) syncytiotrophoblast has been identified as the prinicipal site of progesterone synthesis in the placenta of the guinea-pig. This was evident from the relatively large amounts of progesterone synthesized by the SZ from [7alpha-3H]pregnenolone and the exact correlation of SZ development and the estimated progesterone secretory activity of the placenta throughout gestation. Placental progesterone secretion started between days 20--25 of gestation when the SZ was being formed. Progesterone secretion rose to a maximum by day 30 and was maintained until at least day 53, reflecting the large amount of SZ tissue present in the placenta during this period. Secretory activity decreased simultaneously with decrease in SZ tissue, even though a decrease in progesterone concentration in systemic plasma was not evident. The results also suggested that the yolk sac was able to synthesize progesterone and metabolize steroids in vitro. Small quantities of 5-saturated C21 steroids were also synthesized by the placenta.
TL;DR: Little if any de novo synthesis of cholesterol occurs in mid-gestation placenta, but great species differences in bio-transformation of steroids may occur and the inhibition of estrogen biosynthesis by steroids will be considered.
TL;DR: The unusually high levels of 17α-hydroxyprogesterone in marmosets is in contrast to that observed in other mammalian species.