Regulation of squalene synthetase activity in rat liver: elevation by cholestyramine, but no diurnal variation.
Squalene synthetase activity in liver microsomes from rats sacrificed at three different times of the diurnal cycle showed no significant differences. Addition of 4% cholestyramine to the food resulted in a marked increase in activity (280% of control), independent of the time of killing. 3-Hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol 7 alpha-hydroxylase activity, determined as positive controls, were also found to be elevated by cholestyramine and additionally showed a diurnal variation. On the other hand, five control enzyme activities, not directly related to cholesterol metabolism, i.e. glutamate dehydrogenase, NADPH cytochrome-c reductase, beta-hexosaminidase, catalase and acyl coenzyme A oxidase, showed neither an influence of cholestyramine feeding nor a time of sacrifice dependent variation.
D000818:Animals; D002374:Catalase / Q000378:metabolism; D002790:Cholesterol 7-alpha-Hydroxylase / Q000378:metabolism; D002792:Cholestyramine Resin / Q000494:pharmacology*; D002940:Circadian Rhythm; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000378:metabolism*; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D006596:Hexosaminidases / Q000378:metabolism; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013185:Squalene / Q000378:metabolism; D001619:beta-N-Acetylhexosaminidases
D002792:Cholestyramine Resin; D013185:Squalene; D010088:Oxidoreductases; D006903:Hydroxymethylglutaryl CoA Reductases; D002374:Catalase; D002790:Cholesterol 7-alpha-Hydroxylase; D005969:Glutamate Dehydrogenase; D009251:NADPH-Ferrihemoprotein Reductase; D013186:Farnesyl-Diphosphate Farnesyltransferase; D006596:Hexosaminidases; D001619:beta-N-Acetylhexosaminidases