Identification of regulatory oxysterols, 24(S),25-epoxycholesterol and 25-hydroxycholesterol, in cultured fibroblasts.
Biosynthetically tritiated sterols from Chinese hamster lung (Dede) cells were fractionated by high performance liquid chromatography, and fractions were assayed for their ability to repress 3-hydroxy-3-methylglutaryl-CoA reductase in L cell cultures. Most of the activity found was associated with two oxysterols, 24(S),25-epoxycholesterol and 25-hydroxycholesterol. The identities of the two sterols were established by co-chromatography with authentic samples and by isotopic dilution and recrystallization. Only low levels of repressor activity were found in other fractions of the sterol extract. The endogenous concentrations of 24(S),25-epoxycholesterol (7.2 fg/cell) and 25-hydroxycholesterol (1.5 fg/cell) appear to be within the ranges required for the regulation of HMG-CoA reductase.
D000818:Animals; D002417:Cattle; D002460:Cell Line; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000096:biosynthesis; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D006224:Cricetinae; D003412:Cricetulus; D003470:Culture Media; D004794:Enzyme Repression; D005333:Fetus; D005347:Fibroblasts / Q000378:metabolism; D006888:Hydroxycholesterols / Q000096:biosynthesis* / Q000302:isolation & purification / Q000494:pharmacology; D006903:Hydroxymethylglutaryl CoA Reductases / Q000096:biosynthesis; D008168:Lung; D008798:Mevalonic Acid / Q000378:metabolism; D014316:Tritium
D003470:Culture Media; D006888:Hydroxycholesterols; D014316:Tritium; C028358:24,25-epoxycholesterol; C007997:25-hydroxycholesterol; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D008798:Mevalonic Acid