Influence of type IIa, IIb and IV-hyperlipoproteinemia on platelet prostaglandin sensitivity, plasma thromboxane B2 and platelet half-life.

It is generally accepted that in hyperlipoproteinemia (HLP) the vascular prostacyclin formation is diminished. We wondered, whether HLP is also associated with changes in platelet sensitivity to antiaggregatory prostaglandins. Therefore, we examined the platelet sensitivity to the prostaglandins PGI2 and PGD2 as well as plasma thromboxane B2 (TXB2)-levels in 24 patients with HLP type IIa, IIb and IV. We found a marked decrease of platelet sensitivity to PGI2 in all the patients examined, which was more pronounced in type IIb than in types IIa and IV. Platelet sensitivity to PGD2 showed no difference in the hyperlipemic patients. Plasma TXB2-levels were significantly increased in comparison to a control group, the changes being most pronounced in patients with type IV HLP. Platelet half-life was significantly shortened in the HLP-patients. This in-vivo platelet function parameter was found to be reduced in patients with type IIa HLP to the greatest extent. Our findings suggest that platelet deposition in HLP is promoted not only by diminished vascular PGI2-formation, but also by decreased sensitivity of the platelets to antiaggregatory prostaglandins. The high TXB2-levels and the shortened platelet half-life reflect the in-vivo activated platelet population in these patients.