Platelet activation and platelet-erythrocyte aggregates in end-stage renaldisease patients on hemodialysis

Activated platelets may eng-age in dynamic interplay with other blood cells . We examined the evidence for platelet activation and the formation of pla telet-erythrocyte aggregates in chronic hemodialysis patients. Circulating activated platelets (P-selectin/CD63-positive platelets) were higher than n ormal controls (p < 0.001) and further increased during hemodialysis sessio ns, the increase being higher when patients were dialyzed with cellulosic t han with synthetic membranes. We found direct evidence of uremic platelet-e rythrocyte adherence in vitro and increased levels of circulating platelet- erythrocyte aggregates in dialysis patients, which represents a new observa tion in uremia. Platelet-erythrocyte aggregates were subject to further inc rease during hemodialysis, and again higher levels were found with cellulos ic than synthetic membranes. This phenomenon was reproduced in vitro by bot h ADP and PAF. but not by either complement factor C3a or by heparin concen trations corresponding to those used for clinical hemodialysis. We conclude that platelet-erythrocyte aggregates occur in hemodialysis patients probab ly owing to a primary platelet activation mechanism.