Pregnenolone

About: Pregnenolone is a research topic. Over the lifetime, 3539 publications have been published within this topic receiving 126444 citations. The topic is also known as: (3b)-3-hydroxy-Pregn-5-en-20-one & 3-Hydroxypregn-5-en-20-one.

Inhibition of Testosterone Production by Propylthiouracil in Rat Leydig Cells

Abstract: Propylthiouracil (PTU) is a thioamide drug used clinically to inhibit thyroid hormone production. However, PTU is associated with some side effects in different organs. In the present study, the acute and direct effects of PTU on testosterone production in rat Leydig cells were investigated. Leydig cells were isolated from rat testes, and an investigation was performed on the effects of PTU on basal and evoked-testosterone release, the functions of steroidogenic enzymes, including protein expression of cytochrome P450 side-chain cleavage enzyme (P450scc) and mRNA expression of the steroidogenic acute regulatory protein (StAR). Rat Leydig cells were challenged with hCG, forskolin, and 8-bromo-cAMP to stimulate testosterone release. PTU inhibited both basal and evoked-testosterone release. To study the effects of PTU on steroidogenesis, steroidogenic precursor-stimulated testosterone release was examined. PTU inhibited pregnenolone production (i.e., it diminished the function of P450scc in Leydig cells). In addition to inhibiting hormone secretion, PTU also regulated steroidogenesis by diminishing mRNA expression of StAR. These results suggest that PTU acts directly on rat Leydig cells to diminish testosterone production by inhibiting P450scc function and StAR expression. cyclic adenosine monophosphate, Leydig cells, signal transduction, testosterone, toxicology

In Vitro biosynthesis of steroids from cholesterol by the ovaries and pyloric caeca of the starfish Asterias rubens

Abstract: 1. 1. In vitro biosynthesis of steroids from cholesterol in ovaries and pyloric caeca of Asterias rubens has been investigated. 2. 2. The formation of pregnenolone and progesterone was demonstrated in both tissues by using 1,2-3H-cholesterol as a precursor. 3. 3. Pregnenolone and progesterone are produced in small quantities; the ovaries appear to be more active in the biosynthesis of these steroids than the pyloric caeca. 4. 4. The results indicate the presence of the following biosynthetic enzyme systems in ovaries and pyloric caeca of Asterias rubens: a side-chain-cleaving enzyme complex and a Δ 5 –Δ 4 - isomerase -3β- HSD complex. 5. 5. The importance of these enzymes and the function of cholesterol for the biosynthesis of steroids will be discussed.

Effects of Chronic Treatment with a Potent Luteinizing Hormone Releasing Hormone Agonist on Serum Luteinizing Hormone and Steroid Levels in the Male Rhesus Monkey

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.

The Control of Steroidogenesis by Human Fetal Adrenal Cells in Tissue Culture. I. Responses to Adrenocorticotropin

Abstract: A technique of monolayer tissue culture of human fetal adrenal cells was developed in order to study steroidogenic responses to factors such as ACTH. The daily production of 12 steroids [pregnenolone, 17-hydroxy pregnenolone, dehydroepiandrosterone (DHA), DHA sulfate, progesterone, 17-hy-droxyprogesterone, aridrostenedione, testosterone, corticoster-one, 11-desoxycortisol, cortisol, and aldosterone) was measured by RIA. Initially, fresh’fetal adrenal cells produced DHA, DHA sulfate, 17-hydroxypregnenolone, and small amounts of cortisol, but in _he absence of ACTH, the production of all steroids declined during culture to low levels. The addition of physiological amounts (1–104 pg/ml) of either αACTH-(l–24) or αACTH-(1–39) or coculture with fetal pituitary cells elicited a progressive rise in steroid production during the first 4–6 days of incubation. The lowest ACTH doses elicited a proportionately greater adrenal androgen response (as reflected in the DHA to cortisol ratio), but with increasing ACTH dosa...

The Radioimmunoassay of Testosterone, 5α-Dihydrotestosterone and Their Precursors in the Human Testis

Abstract: A method is described for the simultaneous radioimmunoassays of pregnenolone, progesterone, 17α-hydroxyprogesterone, androstenedione, testosterone and 5α-dihydrotestosterone in 100 mg samples of human testis tissue. The specificity is illustrated by determining the chromatographic elution profiles of steroid extracts by radioimmunoassay. The C.V. of individual assays were assessed by analysing 5 samples taken from the same testis, and illustrates the high reproducibility of the method, and homogeneity of samples. The stability of endogenous testicular steroids was assessed in relation to time at room temperature, and marked changes in composition occurred within 5 h, indicating the limitations in using autopsy samples. Testicular steroid concentrations were determined in testes from 16 patients, 10 of whom had been treated with estrogen (polyestradiol phosphate) 1–5 days before orchiectomy. No effect of estrogen treatment on testicular concentrations of steroids was observed, despite the previously established decline in levels of these steroids in the spermatic veins of similar patients.