Platelet plasma-membrane changes in human type IIa hypercholesterolemia

We have examined platelets collected from hypercholesterolemic (HC) young patients (n = 12) and from normocholesterolemic young volunteers (n = 9) by means of freeze fracture. The mean value of the surface density per square micrometer of the openings of the surface-connected canalicular system (SCCS) was significantly higher (p less than 0.03) in the HC patients (2.4 +/- 0.6) compared with the controls (1.8 +/- 0.5), likewise in the hypercholesterolemic diet-induced rabbits as previously reported by us. In the patients, the SCCS increase was positively correlated with the low-density lipoprotein cholesterolemia/total cholesterol ratio (p < 0.005) and inversely correlated with the high-density lipoprotein cholesterolemia/total cholesterol ratio (p less than 0.01). These data indicate that the circulating platelets of HC type IIa patients appear changed at ultrastructural level and that their modification are related to platelet activation and the atherogenetic processes