Studies on the formation of C7-oxygenated cholesterol and beta-sitosterol metabolites in cell-free preparations of rat liver.
The microsomal fraction and the 18,000 g supernatant fluid obtained from livers from normal rats, cholestyraminetreated rats, or from rats with a bile fistula have been used to compare the 7alpha-hydroxylation of [4-(14)C]cholesterol and beta-[4-(14)C]sitosterol (24alpha-ethyl-cholesterol). It was not possible to increase the specific formation of 7alpha-hydroxy-beta-sitosterol above 0.05% with any of the preparations. This conversion was less than 1% of that found for cholesterol. The inhibitory effect of added 7-oxo- and 7beta-hydroxy-beta-sitosterol on the 7alpha-hydroxylation of cholesterol was found to be much less than that of the corresponding cholesterol compounds. 7alpha-Hydroxy-beta-sitosterol was without effect. It is concluded that the activity of the cholesterol 7alpha-hydroxylase is dependent upon the structure of the steroid side chain.
D000818:Animals; D001658:Biliary Fistula / Q000378:metabolism; D002247:Carbon Isotopes; D002474:Cell-Free System; D002784:Cholesterol / Q000378:metabolism*; D002792:Cholestyramine Resin / Q000494:pharmacology; D002849:Chromatography, Gas; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D002940:Circadian Rhythm; D006900:Hydroxylation; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology; D010840:Phytosterols / Q000378:metabolism*; D051381:Rats; D012855:Sitosterols / Q000378:metabolism / Q000494:pharmacology; D013250:Steroid Hydroxylases / Q000378:metabolism; D013997:Time Factors; D014304:Triolein / Q000494:pharmacology
D002247:Carbon Isotopes; D010840:Phytosterols; D012855:Sitosterols; D002792:Cholestyramine Resin; D014304:Triolein; D002784:Cholesterol; D013250:Steroid Hydroxylases; D010634:Phenobarbital