Lipoprotein levels and tissue lipids in fatty-fibrous atherosclerosis induced in rabbits by two years' cholesterol feeding at a low level.

A group of 12 young NZW rabbits of the same breeding strain were fed a diet enriched with 0.1% cholesterol by weight. The resulting modest hypercholesterolaemia resolved after 4-5 months. Two animals that died during this period showed no gross or microscopic atherosclerosis. After 6 months, the dietary cholesterol was increased to 0.2%. In some animals this resulted in moderate hypercholesterolaemia. One animal that died at this time showed no atherosclerosis with a mean serum cholesterol level of 224 mg/dl. Just after one year, dietary cholesterol was increased to 0.3%. This resulted in definite hypercholesterolaemia in some animals, but a few resisted the treatment with mean serum cholesterol levels around 40-60 mg/dl. In general, animals with established hypercholesterolaemia showed severe atherosclerosis, but often of a more fibrous and less cellular nature than is usual in the rabbit. Aortic wall cholesterol content (on a weight basis) correlated positively with serum cholesterol concentration (r = + 0.69, P approximately 0.05) and negatively with the ratio of HDL cholesterol to (LDL plus VLDL) cholesterol (double log plot: r = -0.79, P less than 0.025).