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.

The Hydrolysis of Estrone Sulfate and Dehydroepiandrosterone Sulfate by MCF-7 Human Breast Cancer Cells*

Abstract: Reports of estrone (E1) and dehydroepiandrosterone (DHEA) sulfatase (sulfohydrolase) activities within many human breast cancers have prompted us to undertake the identification and partial characterization of these enzyme activities within MCF-7 human breast cancer cells. Enzyme assays were performed within subcellular preparations and intact cultures by quantifying the total nonpolar 3H-labeled metabolites formed from [3H]E1 sulfate (E1S) and [3H]DHEA sulfate (DHEAS). The results have shown that the hydrolysis of each steroid sulfate is mediated by different particulate enzymes, which demonstrate optimal activity between pH 6.0–7.0. The analysis of enzyme kinetic data showed the Km values of E1S and DHEAS for their enzymes to be approximately 6.3 and 3.6 μM/L, respectively. Neither enzyme was subject to product inhibition. Androsterone sulfate and pregnenolone sulfate produced significant inhibition of E1, but not DHEA, sulfatase activity. E1S inhibited DHEA sulfatase competitively, with an approximate ...

Bacterially produced apolipoprotein D binds progesterone and arachidonic acid, but not bilirubin or E-3M2H.

Abstract: Apolipoprotein D (ApoD) constitutes an atypical lipoprotein in so far as it is predominantly found associated with HDL particles but belongs to the lipocalin structural family. Apart from its involvement in serum lipid transport it is abundant in various tissues, and differing physiological functions have been ascribed to it. We have now developed an E. coli expression system that permits the efficient production of biochemically homogeneous ApoD via secretion into the bacterial periplasm. Detailed ligand binding studies by fluorescence titration revealed that progesterone and arachidonic acid are complexed with dissociation constants both in the 1 microM range, whereas the presumed ligands pregnenolone, bilirubin and E-3M2H are not recognized by the recombinant protein. In contrast with previous reports it thus appears that ApoD discriminates well in its binding function between closely related compounds.

Developmentally regulated expression of adrenal 17 alpha-hydroxylase cytochrome P450 in the mouse embryo.

Abstract: Corticosterone is the major circulating glucocorticoid in adult mice and rats, and this is explained, in part, by the absence of 17 alpha-hydroxylase cytochrome P450 (P450c17) in adrenal glands of these rodents. During embryonic development, however, we discovered transient expression of P450c17 in a subset of adrenocortical cells in the fetal mouse adrenal. This differs from cholesterol side-chain cleavage cytochrome P450 and adrenodoxin, which are expressed continuously in most fetal adrenocortical cells from onset of expression at embryonic days 11-12 (E11-12) until term. Adrenal P450c17 transcripts are detectable in situ at E12.5 and increase in abundance from E12.5 to E14.5. Transcripts are then lost between E16.5 and term (E18.5) and are undetectable in situ in adrenal glands of adult mice. These results are consistent with the presence of pregnenolone 17 alpha-hydroxylase activity in adrenal homogenates of fetal but not adult mice. By using polymerase chain reaction, we determined that murine fetal...