STUDIES ON THE PROGRESSION AND REGRESSION OF CORONARY AND PERIPHERAL ATHEROSCLEROSIS IN THE CYNOMOLGUS MONKEY .1. EFFECTS OF DIPYRIDAMOLE AND ASPIRIN

The morphological and biochemical changes in the arteries of the cynomolgus monkey were investigated during the induction and regression of atherosclerosis. During the feeding of an atherogenic diet containing 2% cholesterol and 10% butter for 5 months, the animals developed fibro-fatty plaques which involved the coronary and peripheral arteries and caused significant luminal narrowing of these vessels. The induced aortic lesions contained increased amounts of free and esterified cholesterol, collagen, elastin, and calcium. These changes were associated with an elevation of plasma cholesterol and an increased net influx of plasma cholesterol and LDL into the aorta. Dipyridamole (10 mg/kg) and aspirin (50 mg/kg) had no effect on the arterial uptake of plasma LDL and cholesterol and did not protect against atherosclerosis in any of the vessels examined. During the regression period (low cholesterol diet) of 12 months duration, the induced lesions became more fibrotic and calcified while the cellularity and lipid content of the same lesions decreased. As a result of these changes there were no significant decreases in the atherosclerotic narrowing of the coronary and peripheral vessels. The net influx of plasma LDL and cholesterol into the aorta returned to normal during the regression period. This finding together with the slow rate of aortic cholesterol equilibration suggests that the retention of cholesterol in the regressed aortic lesions is due to a defect in cholesterol transport rather than to an abnormality in intimal permeability. The addition of dipyridamole and aspirin to the regression diet did not alter the course of the atherosclerosis. © 1979.