The effect of ileal bypass on atherosclerosis and hypercholesterolemia in the rabbit

White New Zealand rabbits were divided into four groups: Group I (controls) fed standard rabbit pellets for 4 months; Group II fed a 2 percent cholesterol diet for 4 months; Group III fed a 2 percent cholesterol diet for 4 months subsequent to ileal bypass surgery; and Group IV subjected to ileal bypass after 4 months on the 2 percent cholesterol diet and then continued on the diet and followed for periods up to 15 months. Group I rabbits exhibited no hypercholesterolemia or atherosclerosis. Group II animals had an average blood cholesterol level of 1,265 mg. percent and were severely atherosclerotic, as shown by a 50 percent myocardial infarction rate. Group III rabbits retained cholesterol values below that of the controls and showed no evidence of atherosclerosis. Group IV animals, if permitted to survive 6 months or longer subsequent to a fall in cholesterol levels below 100 mg. percent, showed no progression of acute atherosclerosis, but evidenced regression of liver, spleen, and kidney foam cell and cholesterol accumulations; and fibrosis of established intimal plaques, with a total aorta cholesterol content per residue weight 33.8 percent lower than that of Group II, and possibly fewer plaques than at the height of their atherosclerosis.