title: Regulation of hepatic receptor-dependent degradation of LDL by mevinolin in rabbits with hypercholesterolemia induced by a wheat starch-casein diet.
abstract: Rabbits fed a wheat starch-casein diet develop a marked hypercholesterolemia and have a slower rate of removal of rabbit 125I-labeled low density lipoproteins (LDL) from plasma. Treating rabbits with mevinolin, a highly potent competitive inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, at a daily dose of 20 mg per animal prevents the increase in plasma and LDL cholesterol. The mevinolin effect is mediated through an increased rate of removal of rabbit 125I-labeled LDL from plasma. To study the role of mevinolin on the regulation of the hepatic LDL receptor in rabbits, the binding of 125I-labeled LDL and 125I-labeled beta-VLDL (beta-migrating very-low-density lipoproteins) to liver membranes prepared from rabbits fed the wheat starch-casein diet with or without mevinolin was investigated. Liver membranes from wheat starch-casein-fed rabbits have no demonstrable EDTA-sensitive binding activity of 125I-labeled LDL and low (37 ng/mg protein) binding activity of 125I-labeled beta-VLDL. Treatment of the wheat starch-casein fed rabbits with mevinolin results in high levels of specific EDTA-sensitive binding of 125I-labeled LDL (28.7 ng/mg protein) and 125I-labeled beta-VLDL (120 ng/mg protein). To assess the functional role of the hepatic LDL receptor in response to mevinolin, the catabolism of 125I-labeled LDL by perfused rabbit livers was studied. Perfused livers from mevinolin-treated rabbits show a 3.3-fold increase in the rate of receptor-dependent catabolism of 125I-labeled LDL (4.6% X h-1) when compared with that of livers from rabbits not treated with mevinolin (1.4% X h-1). Thus, these studies demonstrate that mevinolin prevents the increase of plasma LDL cholesterol level in rabbits fed a wheat starch-casein diet by regulating the levels of hepatic LDL-binding sites and the rate of receptor-dependent catabolism of LDL by the liver.
mesh_terms: D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D002364:Caseins / Q000494:pharmacology; D004032:Diet; D006937:Hypercholesterolemia / Q000209:etiology / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008148:Lovastatin; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology*; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011973:Receptors, LDL; D013213:Starch
chemical_list: D000924:Anticholesteremic Agents; D002364:Caseins; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D009281:Naphthalenes; D011956:Receptors, Cell Surface; D011973:Receptors, LDL; D013213:Starch; D008148:Lovastatin