Non-esterified cholesterol-rich adrenal lipid fractions. Preparation, properties and preferential utilization for cholesterol side-chain cleavage by corticotropin-stimulated adrenal mitochondria.
Rat adrenal 105,000 g supernatant contains two lipid moieties, 'lipid-I' and 'lipid-II' which contain non-esterified cholesterol and stimulate cholesterol side-chain cleavage in soluble or mitochondrial enzyme systems. Lipid-I contains relatively large low-density heat-stable particles, whereas lipid-II particles are smaller, more dense and heat-labile. Lipid-I and lipid-II can be separated from clear cytosol by ultracentrifugation and gel filtration respectively. Corticotropin plus cycloheximide treatment increases the non-esterified cholesterol concentrations in the lipid fractions, and stimulatory effects of lipids on cholesterol side-chain cleavage appear to correlate with non-esterified cholesterol concentrations therein. On addition of saturating amounts of cholesterol-rich lipid, pregnenolone synthesis and cholesterol binding to cytochrome P-450 are stimulated more in mitochondria from corticotropin-stimulated adrenals than in mitochondria from control or corticotropin-plus cycloheximide-stimulated adrenals. These results support the contention that the corticotropin-induced increase in mitochondrial cholesterol side-chain cleavage involves an increase in cholesterol utilization as well as an increase in cholesterol availability.
D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D002784:Cholesterol / Q000378:metabolism*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism; D002850:Chromatography, Gel; D003513:Cycloheximide / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D066298:In Vitro Techniques; D050356:Lipid Metabolism; D008055:Lipids / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D011284:Pregnenolone / Q000096:biosynthesis; D051381:Rats
D008055:Lipids; D011284:Pregnenolone; D000324:Adrenocorticotropic Hormone; D002784:Cholesterol; D003513:Cycloheximide; D002786:Cholesterol Side-Chain Cleavage Enzyme; D002118:Calcium