Platelet function and survival in rats with genetically determined hypercholesterolaemia.

Platelets from rats with genetically determined hypercholesterolaemia are hypersensitive to aggregation induced by thrombin compared with platelets from their genetic controls without hypercholesterolaemia. Aggregation or release induced by thrombin of platelets from hypercholesterolaemic and control rats correlated significantly with plasma cholesterol concentrations. Platelet responses to ADP or collagen were not different between the groups. The hypersensitivity to thrombin-induced aggregation was independent of released ADP or products of arachidonic acid metabolism. The changes in platelet sensitivity occurred with only moderate increases in plasma cholesterol concentration and with no detectable changes in total platelet cholesterol. The hypersensitivity of platelets from hypercholesterolaemic rats was not associated with a reduction in platelet survival or any significant injury to the aortic endothelium in these animals. Platelets from hypercholesterolaemic rats were smaller than platelets from controls. Thus, platelets from rats with genetically determined hypercholesterolaemia have alterations in function similar to those found with platelets from rats with diet-induced hypercholesterolaemia indicating that this strain can be used to study the mechanisms by which cholesterol can change platelet function without the possible complicating effects of dietary factors. Since platelet hypersensitivity occurred in rats with genetically determined hypercholesterolaemia without a reduction in platelet survival, these studies are also consistent with the reduced platelet survival found in animals with diet-induced hypercholesterolaemia being independent of platelet changes.