[Enhancement of platelet function in cholesterol-fed guinea-pigs]

Effects of cholesterol-loading on platelet functions were studied. Guinea-pigs were fed on a diet containing 1% cholesterol for 1--5 months. Cholesterol-feeding caused an elevation of cholesterol content in the plasma and platelets, although the phospholipids increased only in the plasma. Enhanced platelet aggregation induced by ADP, collagen, and arachidonic acid was maintained for 5 months during cholesterol-feeding, concomitant with an increase in malondialdehyde production in platelets. Although basal levels of platelet cyclic AMP were not affected, PGE1-stimulated cyclic AMP levels were markedly decreased in platelets of cholesterol-fed animals. The same results were observed in platelets treated with theophylline. No change in the generation of PGI2-like substance by the aortic tissue occurred during 4 months of cholesterol-feeding, though a significant increase was seen after 5 months. These results suggest that the enhancement of platelet function by cholesterol-feeding is concerned with enhanced prostaglandin synthesis and suppressed adenylate cyclase activity in platelets.