PLASMA ACTIVITIES OF LECITHIN - CHOLESTEROL ACYLTRANSFERASE, LIPID TRANSFER PROTEINS AND POSTHEPARIN LIPASES IN INBRED STRAINS OF RABBITS HYPO-RESPONSIVE OR HYPER-RESPONSIVE TO DIETARY-CHOLESTEROL

Plasma lipoproteins, plasma activities of lecithin: cholesterol acyltr ansferase (LCAT), phospholipid transfer protein (PLTP), cholesteryl es ter transfer protein (CETP) and post-heparin lipases were measured bef ore and after cholesterol challenge in two inbred strains of rabbits w ith either a high (hyper-responders) or a low (hyporesponders) respons e of plasma cholesterol to dietary cholesterol. The purpose of this st udy was to provide clues about the mechanisms underlying the effect of dietary cholesterol on lipoprotein levels and composition, and partic ularly those underlying the strain difference of this effect. Choleste rol feeding (0.15 g of cholesterol/100 g of diet) caused increased pla sma total cholesterol concentrations and an increased ratio of cholest eryl esters:triacylglycerol in all lipoprotein particles in both strai ns; these effects were significantly greater in hyper- than hyporespon sive rabbits. Feeding on the high-cholesterol diet lowered plasma tria cylglycerols in hyper-responders, but caused increased plasma triacylg lycerol levels in hyporesponders. This was accompanied by significantl y greater increases in the activities of hepatic triacylglycerol lipas e and lipoprotein lipase in hyper- than in hypo-responders. Both strai ns showed a dietary-cholesterol cholesterol-induced rise in plasma CET P as well as in PLTP activity. The increase in PLTP activity was great er in the hyper-responders, but that of CETP was less. There was no ef fect of dietary cholesterol on LCAT activity. It is hypothesized that the lipases are involved in the removal of cholesterol-rich lipoprotei ns.