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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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Journal ArticleDOI
TL;DR: It is proposed that cytochalasin B enhances the availability of cholesterol bound to HDL for steroidogenesis by Y-1 adrenal cells by increasing the levels of cAMP at concentrations that lead to maximal steroidogenesis.
Abstract: The cytochalasins stimulate steroid secretion of Y-1 adrenal tumor cells two-to threefold. The order of potencies is cytochalasin E is greater than D is greater than B, but the maximum response is the the same and always less than with ACTH. Like that with ACTH, the stimulation has a rapid onset, is easily reversible, is inhibited by cucloheximide and aminoglutethimide, and occurs at a stage before pregnenolone. Although the cytochalasin, like ACTH, produce cell rounding, it is shown that this morphological change is not necessarily coupled to steridogenesis. Unlike ACTH, cytochalasin B does not measurably increase cellular levels of cAMP at concentrations that lead to maximal steroidogenesis. The cytochalasin B-induced stimulation of steroidogenesis, unlike the short-term ACTH effect, fails to occur in the absence of serum. This lack of response can be corrected by even low concentrations of human high density lipoproteins (HDL) but not by low density lipoproteins (LDL). We, therefore, propose that cytochalasin B enhances the availability of cholesterol bound to HDL for steroidogenesis by Y-1 adrenal cells.

47 citations

Journal Article
TL;DR: It is demonstrated in the hippocampus that locally synthesized estrogen rapidly enhances the synaptic plasticity of neurons, and that BPA and DES modulate the synaptic Plasticity as well as the synthesis of estradiol.
Abstract: The mechanisms of neurosteroid synthesis in the rat hippocampus were investigated. Metabolism assay demonstrated the pathway of "cholesterol alpha pregnenolone --> dehydroepiandrosterone --> androstenedione --> testosterone --> estradiol." Upon exposure of pups to bisphenol A (BPA) from the embryonic stage until 3 week-old stage, a significant facilitation of the synthesis of estradiol was observed in the hippocampus. The localization of cytochrome P450s (P450scc, P45017alpha, and P450arom) as well as estrogen receptor alpha (ER(alpha)) was observed in pyramidal and granule neurons, using immunohistochemical staining. Furthermore, the synaptic localization of P45017alpha, P450arom and ER(alpha) was demonstrated with immuno-electron microscopic analysis. The acute action of estradiol and endocrine disrupters were then analyzed with an electrophysiological measurement of hippocampal pyramidal neurons. A 30 min preperfusion of diethylstylbesterol (DES) enhanced the induction of long-term potentiation (LTP) by almost an identical magnitude to that obtained by estradiol perfusion. On the other hand, although the application of BPA alone did not affect LTP-induction, the co-perfusion of BPA with estradiol completely suppressed the enhancement effect of LTP by estradiol. The current investigations demonstrate in the hippocampus (1) that locally synthesized estrogen rapidly enhances the synaptic plasticity of neurons, and (2) that BPA and DES modulate the synaptic plasticity as well as the synthesis of estradiol. The probable targets of BPA and DES are ER(alpha) and steroidogenic proteins.

47 citations

Journal ArticleDOI
01 Jan 1971-Steroids
TL;DR: O,p′-DDD blocked dibutyryl cyclic AMP-induced steroidogenesis, indicating that the drug acts after the generation of cyclic-3′,5′-AMP, and the site of action appears to be on the ACTH-regulated intramitochondrial conversion of cholesterol to pregnenolone.

47 citations

Journal ArticleDOI
TL;DR: Inhibition of local glucocorticoid biosynthesis in thymi from TCR transgenic mice during fetal thymic organ culture (FTOC) revealed significant alterations in the process of thymocyte selection, suggesting that glucoc Corticoids do not simply suppress the immune system but rather are necessary for thymocytes survival and differentiation.
Abstract: T cells undergo rigorous selection processes in the thymus that are necessary to prevent T cells with either autoreactive or nonfunctional T-cell receptors (TCRs) from entering the periphery. Although both positive and negative selection depend on TCR-mediated signals, the means by which a thymocyte interprets these signals to result in survival or death is not understood. Glucocorticoids are known to induce thymocyte apoptosis at high concentrations, but at lower concentrations glucocorticoids can antagonize TCR-mediated deletional signals and allow survival of thymocytes and T cell hybridomas. Interestingly, transgenic mice in which the expression of the glucocorticoid receptor has been downmodulated specifically in thymocytes have abnormal thymocyte differentiation, indicating that glucocorticoids play a significant role in T-cell development. Furthermore, we have demonstrated the presence of steroidogenic enzymes in the thymic epithelium and can show that, in vitro, these cells readily synthesize pregnenolone, the first product in the steroidogenic pathway, and deoxycorticosterone. Inhibition of local glucocorticoid biosynthesis in thymi from TCR transgenic mice during fetal thymic organ culture (FTOC) revealed significant alterations in the process of thymocyte selection. These data suggest that glucocorticoids do not simply suppress the immune system but rather are necessary for thymocyte survival and differentiation.

47 citations

Journal ArticleDOI
TL;DR: The rate that cholesterol traverses the contact point to reach the inner membrane is accelerated by the steroidogenic acute regulatory protein, and newly synthesized steroid hormones are transported to the cell periphery for export via a mechanism that may utilise an ion exchange protein.
Abstract: Steroidogenic tissue can respond almost immediately to a stimulatory hormonal stimuli. Recent findings are shedding light on the molecular and cellular mechanisms that are used to synthesize and export steroid hormones in the acute phase of stimulation. In addition to utilising the cAMP intracellular messenger system to convey a stimulatory message, steroidogenic cells may employ the protein kinase C, arachidonic acid, tyrosine phosphate and nitrous oxide systems. It has been proposed that cholesterol laden vesicles travel along a network of intermediate filaments to reach the mitochondria. Cholesterol may then translocate from the outer mitochondrial membrane to the inner via sites of contact between the two membranes. These contact sites may be composed of protein bridges which include the constituents, porin, the benzodiazepine receptor and GTP binding proteins. Cholesterol is transported through the contact sites to the inner membrane and on reaching cytochrome P450 side chain cleavage (P450scc), cholesterol is converted to pregnenolone. Pregnenolone is in turn converted to a range of steroid hormones via enzyme casades. GTP binding proteins may regulate the contact site between the inner and outer membranes and thereby modulate cholesterol flux to P450 scc. In the adrenal and gonads the rate that cholesterol traverses the contact point to reach the inner membrane is accelerated by the Steroidogenic acute regulatory protein. Newly synthesized steroid hormones are transported to the cell periphery for export via a mechanism that may utilise an ion exchange protein.

47 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
202255
202124
202028
201950
201835