Topic
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.
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TL;DR: There is a distinct shift in the steroidogenic pathway from estradiol-17&b gr; to 17&agr;, 20&bgr;-DP production in medaka ovarian follicles, and it is suggested that the decrease in C17, 20-lyase activity is responsible for this shift.
Abstract: Changes in the steroidogenic pathway in medaka (Oryzias latipes) ovarian follicles during vitellogenesis and oocyte maturation were investigated in vitro by incubation of follicles with several radiolabeled steroid precursors, followed by thin layer chromatography (TLC) fractionation and recrystallization. When vitellogenic follicles collected at 18 hr before the expected time of spawning were incubated with 3H-labeled pregnenolone, the major metabolites were 17α-hydroxypregnenolone, 17α-hydroxyprogesterone, and androstenedione. Incubations of vitellogenic follicles with androstenedione produced testosterone and estradiol-17β By contrast, when maturing follicles (postvitellogenic follicles undergoing maturation) collected at 10 hr before spawning were incubated with 3H-labeled pregnenolone, the major metabolites were 17α-hydroxypregnenolone, 17α-hydroxyprogesterone, and 17α, 20β-dihydroxy-4-pregnen-3-one (17α, 20β-DP, maturation-inducing hormone of medaka); androstenedione was not detected. Neith...
38 citations
TL;DR: A fast and sensitive GC-MS/MS method is proposed to determine pregnenolone, dehydroepiandrosterone (DHEA), testosterone and dihydrotestosterone from human plasma and was validated for imprecision, and recovery and applied in a pilot study in patients with hypercholesterolemia.
38 citations
38 citations
TL;DR: The data in this investigation suggest that the guanylate cyclase-cyclic GMP system plays a role in the mechanism of action of testosterone and its precursors.
Abstract: Both testosterone and cyclic GMP stimulate DNA synthesis. Because cyclic GMP and testosterone seem to have similar actions, the objective of this investigation was to determine if testosterone and its precursors might have part of their mechanism of action through stimulation of guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2], the enzyme that catalyzes the formation of cyclic GMP from GTP. The precursors--namely, progesterone, pregnenolone, 17 alpha-progesterone, 17 alpha-hydroxypregnenolone, androstenedione, and dehydroepiandrosterone--caused a 2- to 3 1/2-fold enhancement of guanylate cyclase activity in rat liver, kidney, skeletal muscle, and ventral prostate at a concentration of 1 microM. These precursors are generated from cholesterol, which had no effect itself on guanylate cyclase activity. Testosterone, 19-nortestosterone, 17-methyltestosterone, and 5 alpha-dihydrotestosterone enhanced guanylate cyclase activity 2- to 5-fold in the same tissues at 1 microM. Etiocholanolone, androsterone, and epiandrosterone, metabolites of testosterone metabolism, enhanced guanylate cyclase activity 1 1/2- to 2-fold at this same concentration. Dose-response relationships revealed that testosterone and its precursors and metabolites had their maximal effect at 1 microM but still had some effect at 0.001 microM. The data in this investigation suggest that the guanylate cyclase-cyclic GMP system plays a role in the mechanism of action of testosterone and its precursors.
38 citations
TL;DR: Dogfish testes were incubated with radioactive progesterone, pregnenolone, and testosterone, and both free and conjugated metabolites were examined, and steroid glucuronide formation was insignificant and very large amounts of solvolysable steroids were isolated from all incubations.
38 citations