SPONTANEOUS PLATELET-AGGREGATION IN WHOLE-BLOOD IS INCREASED IN NON-INSULIN-DEPENDENT DIABETES-MELLITUS AND IN FEMALE BUT NOT MALE-PATIENTSWITH PRIMARY DYSLIPIDEMIA

Increased platelet aggregability has been shown in hypercholesterolemi a, and stirring-induced spontaneous aggregation in whole blood is incr eased in insulin-dependent diabetes mellitus (DM). We have determined spontaneous aggregation in citrated (10 mM) whole blood, from 27 prima ry dyslipidemic patients (DYS; 14F, 13M), 16 male non-insulin-dependen t DM (NIDDM) patients, and 17 normolipidemic controls (N; 6F, 11M), us ing platelet counting to quantify aggregation, Spontaneous aggregation was significantly higher, both in the female DYS group (median 30% [i nterquartile range 25,50], P < 0.005) and the NIDDM group (33% [25,41] , P < 0.005), than in the N group (17% [12,27]), but did not differ si gnificantly in the male DYS group (23% [10,33]). Similar results were obtained in the presence of indomethacin (25 mu mol/l) to prevent arte factual thromboxane (TX) A(2) formation, indicating that increased spo ntaneous aggregation was TXA(2)-independent. Interestingly, increased spontaneous aggregation appeared to be independent of serum cholestero l and triglyceride concentrations, as well as age and sex per se. We c onclude that spontaneous platelet aggregation was increased both in fe male primary dyslipidemic patients and NIDDM patients, but not in male DYS patients. The clinical significance of increased spontaneous plat elet aggregability is that it may favour shear-induced aggregation whi ch may occur at critical arterial stenoses in vivo leading to thrombus formation.