title: Sex-related differences in diurnal activities and development of hepatic microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol 7alpha-hydroxylase.
abstract: The activities of hepatic microsomal 3-hydroxy-3-methylglutaryl CoA reductase and cholesterol 7alpha-hydroxylase were consistently higher (up to 3-fold) in female compared to male rats fed 2% cholestyramine for 8 h daily. In all animals studied, enzymic activities were highest 6 h after feeding began. However, 85% of the rise in cholesterol 7alpha-hydroxylase activity occurred in the 6 h before and 89% of the rise in 3-hydroxy-3-methylglutaryl CoA reductase activity occurred in the 6 h after feeding started. Sex-related differences in both enzymic activities first became apparent at the time of sexual maturity. Enzymic activities before weaning were generally low and a late-suckling (13--20 days) rise in cholesterol 7alpha-hydroxylase was not accompanied by a rise in 3-hydroxy-3-methylglutaryl CoA reductase. For all of these studies we assayed cholesterol 7alpha-hydroxylase at two concentrations of exogenous cholesterol to obviate problems relating to size of the cholesterol pool.
mesh_terms: D000375:Aging; D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D002790:Cholesterol 7-alpha-Hydroxylase / Q000378:metabolism*; D002940:Circadian Rhythm; D004032:Diet; D005260:Female; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D012737:Sex Factors; D013250:Steroid Hydroxylases / Q000378:metabolism*
chemical_list: D001647:Bile Acids and Salts; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase