title: The effect of insulin and catecholamines on the activities of 3-hydroxy-3-methyl glutaryl coenzyme A reductase and acyl-coenzyme A: cholesterol-o-acyltransferase in isolated rat hepatocytes.
abstract: This study was concerned with the effect of insulin and catecholamines on the rate limiting enzymes of cholesterol metabolism in rat hepatocytes. Insulin was found to increase the activity of 3-hydroxy-3-methyl glutaryl coenzyme A reductase and to have no effect on the activity of acyl-coenzyme A: cholesterol-o-acyltransferase. Noradrenaline and isoprenaline increased the activities of both 3-hydroxy-3-methyl glutaryl coenzyme A reductase and acyl-coenzyme A: cholesterol-o-acyltransferase. The effect of noradrenaline or isoprenaline in the presence of insulin was that of a lower stimulatory response on 3-hydroxy-3-methyl glutaryl coenzyme A reductase but comparable to that found with either catecholamine alone. The combination of either catecholamine with insulin had no effect on the activity of acyl-coenzyme A: cholesterol-o-acyltransferase. These observations suggest that the activities of 3-hydroxy-3-methyl glutaryl coenzyme A reductase and acyl-coenzyme A: cholesterol-o-acyl-transferase are regulated independently by insulin in the presence or absence of catecholamines. By contrast, catecholamines appear to regulate both enzyme activities in a similar fashion.
mesh_terms: D000818:Animals; D004347:Drug Interactions; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D002785:Sterol O-Acyltransferase / Q000378:metabolism*
chemical_list: D007328:Insulin; D006903:Hydroxymethylglutaryl CoA Reductases; D002785:Sterol O-Acyltransferase; D007545:Isoproterenol; D009638:Norepinephrine