Renin as a risk factor for atherogenesis. Effects of hypercholesterolemia and two-kidney--one-clip hypertension in the rabbit.

Four groups of New Zealand rabbits were used to study the effect of plasma renin activity (PRA) on atherogenesis. Control groups were fed normal rabbit chow (Group I) or chow supplemented with 0.25% cholesterol and 0.75% corn oil (Group II). The two-kidney--one-clip (2K-1C) hypertensive model was produced in 2 additional groups; Group III (normal diet) and Group IV (atherogenic diet). The latter 2 groups were subgrouped according to PRA levels. Each group was examined over a 7-month period. Group II became hyperlipidemic and developed extensive lipoidal vascular lesions. Mean arterial pressure remained normal throughout the experimental period; PRA fell below normal. Group III and Group IV rabbits developed sustained hypertension irrespective of circulating PRA. The atheromas of Group III were predominantly microscopic and fibromuscular; the extent of aortic and coronary artery involvement was independent of renin response. The most extensive and complicated atheromas were seen in the 2K-1C rabbits consuming the atherogenic diet (Group IV). The lesions were mostly lipoidal, although some were fibromuscular. These results demonstrated that cardiovascular lesions and atherogenesis were exacerbated in the 2K-1C rabbits on a high cholesterol diet; however, PRA was excluded as the cause.