TREATMENT OF CHOLESTEROL-FED RABBITS WITH DIETARY VITAMIN-E AND VITAMIN-C INHIBITS LIPOPROTEIN OXIDATION BUT NOT DEVELOPMENT OF ATHEROSCLEROSIS

New Zealand White rabbits were made hypercholesterolemic by feeding a high cholesterol diet (10 g/kg diet) with or without added antioxidant s. The antioxidants used were either probucol (10 g/kg) or vitamin E ( 10 g/kg) plus vitamin C (0.6 g/kg). Serum cholesterol concentrations w ere monitored as a function of time. At the end of 10 wk, serum and li poprotein vitamin E concentrations, the extent of oxidation of lipopro tein fractions (thiobarbituric acid reacting substances), the suscepti bility of lipoprotein to oxidation in vitro (conjugated diene formatio n) and the extent of atherosclerosis (aortic area stained by Sudan IV and plague thickness) were measured. Rabbits fed diets supplemented wi th vitamins E and C had markedly higher serum vitamin E concentrations , marked vitamin E enrichment in all lipoprotein fractions, less oxida tion in VLDL, and LDL and enhanced resistance of LDL to further in vit ro oxidation, but did not have significantly less aortic atheroscleros is. Rabbits given supplemental probucol likewise exhibited reduced oxi dation of lipoproteins. However, aortic atherosclerosis in these anima ls was significantly lower, as were serum cholesterol concentrations. Inhibition of lipoprotein oxidation itself was not sufficient to reduc e atherosclerosis in cholesterol-fed New Zealand White rabbits.