Platelet deposition at high shear rates is enhanced by high plasma cholesterol levels. In vivo study in the rabbit model.

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Abstract
We have studied the effects of high plasma cholesterol levels on platelet-vessel wall interactions under high shear rate conditions typical of the apex of stenotic arteries (2,600 sec-1). Hypercholesterolemia was induced by feeding rabbits a 0.5% cholesterol-rich diet for 60 days. Platelet deposition was studied by use of an annular perfusion chamber and de-endothelialized abdominal rabbit aortas as substrates. After ingestion of the atherogenic diet, the experimental group of animals developed severe hypercholesterolemia, platelets became more fluid as determined by steady-state fluorescence anisotropy (p less than 0.05), and red blood cell deformability was decreased (p less than 0.001) when compared with normal controls. The fatty acid composition of platelet membranes showed an increase in the percentage of the long-chain saturated fatty acids (palmitic, C16:0, and stearic, C18:0) that may account for the lower polyunsaturated/saturated fatty acid ratio observed in the hyperlipemic animals. Total platelet deposition was significantly increased (p less than 0.05) in the hyperlipemic group as compared with the control group at 5 minutes' perfusion time, becoming less evident at 20 minutes' perfusion time. Our results suggest that the presence of hyperlipidemia may contribute to acute thrombosis by enhancing platelet-vessel wall interaction.