Platelet function and platelet lipid composition in the dyslipoproteinemias.

Blood platelets from eight patients with hyperbetalipoproteinemia (type II) were more reactive to aggregating agents in vitro than those of 13 type IV patients or 12 normal subjects. Platelets of two patients with abeta-lipoproteinemia were also slightly hyperreactive in comparison with normal platelets. However, in one patient with Tangier disease the platelets were distinctly hyporeactive to aggregating agents. Total platelet phospholipid concentration (PL) was elevated in the four groups of patients studied but was highest in the platelets of type IV patients. Platelet-free cholesterol (FC) was significantly higher than normal in all of the dyslipoproteinemias studied. The FC was highest in the two patients with abetalipoproteinemia. The FC/PL molar ratio was normal in all but the abeta-lipoproteinemic patients, in whom it was markedly elevated. Therefore, there is no apparent correlation between FC/PL molar ratio and platelet behavior in vitro. Analysis of individual platelet phospholipids in the four patient groups showed that platelets in Tangier disease had very low concentrations of lysolecithin and phosphatidylinositol (PI) in comparison with normal platelets and the other disease states. Our findings suggest that lysolecithin and phosphatidylinositol may be involved in the structure or function of the sites which modulate platelet response to aggregating agents.