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.

Oocyte maturation in the amago salmon (Oncorhynchus rhodurus): In vitro effects of salmon gonadotropin, steroids, and cyanoketone (an inhibitor of 3β-hydroxy-Δ5-steroid dehydrogenase)

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.

The Influence of Calmodulin on Steroid Synthesis in Ley dig Cells from Rat Testis

Abstract: Two approaches were used to study the possible role of calmodulin in the regulation of synthesis of testosterone by Leydig cells: trifluoperazine was used as an inhibitor of calmodulin and liposomes were used to deliver calmodulin into the cells. The inhibitor prevented the expected responses of Leydig cells to LH and to cAMP. First the increase in synthesis of testosterone produced when these agents are added to Leydig cells was inhibited by the drug. Second, increased transport of cholesterol to mitochondria produced by LH and cAMP was inhibited by trifluoperazine. Third, increased side-chain cleavage of cholesterol (cholesterol leads to pregnenolone) produced by these agents in isolated mitochondria was also inhibited by the drug. When Leydig cells were incubated with liposomes containing calmodulin, production of testosterone, transport of cholesterol to mitochondria, and side-chain cleavage of cholesterol were all stimulated. The effect of calmodulin is greater if Ca2+ is added before incorporation into liposomes than if calmodulin and Ca2+ are introduced into the Leydig cells from separate liposomes. Stimulation of testosterone synthesis does not occur if calmodulin is dialyzed against EGTA, if calmodulin with excess anticalmodulin is present in the liposomes, if either calmodulin or Ca2+ is added to the medium (no liposomes), or if Ca2+ alone is present in liposomes. These observations suggest that calmodulin is involved in regulating the transport of cholesterol to mitochondria, a process that is stimulated by LH and cAMP and one that may account for the increased steroid synthesis produced by these agents.