Measurement of cholesterol 7 alpha-hydroxylase activity with selected ion monitoring.
Formation of 7 alpha-hydroxycholesterol by rat liver microsomes was quantitated using a gas chromatograph-mass spectrometer operated in selected ion monitoring mode. This procedure measures the mass of 7 alpha-hydroxycholesterol formed and does not require addition of labeled cholesterol to monitor the reaction, since endogenous microsomal cholesterol serves as substrate for the enzyme cholesterol 7 alpha-hydroxylase. The method requires only the extraction of lipids from microsomal incubations and injection of a small fraction of this extract into the apparatus. Microsomes from normal rat livers incubated for different periods were found to yield increased 7 alpha-hydroxycholesterol with time.
D000818:Animals; D002790:Cholesterol 7-alpha-Hydroxylase / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006888:Hydroxycholesterols / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D013250:Steroid Hydroxylases / Q000032:analysis*
D006888:Hydroxycholesterols; C011724:cholest-5-en-3 beta,7 alpha-diol; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase