CORRECTION OF THE PLATELET-ADHESION DEFECT IN DELTA-STORAGE POOL DEFICIENCY AT ELEVATED HEMATOCRIT - POSSIBLE ROLE OF ADENOSINE-DIPHOSPHATE

Previous studies on patients with storage pool deficiency (SPD) who ar e specifically deficient in platelet dense granules (delta-SPD) have s uggested a role for dense granule substances, in all likelihood adenos ine diphosphate (ADP), in mediating thrombus formation on subendotheli um at high shear rates. The role of dense granule substances in mediat ing platelet adhesion appears to be more complicated. Previous studies in delta-SPD suggested an adhesion defect that was strongly influence d by the patient's hematocrit (Hct) value. To explore further the poss ibility that red blood cells (RBCs) may influence the role that platel et storage granules play in mediating adhesion at high shear rates, we have measured adhesion (and thrombus formation) throughout a preselec ted range of Hct values (30% to 60%) in normal subjects and in patient s with delta-SPD. The present studies confirm the defect in platelet a dhesion in patients with delta-SPD, most significantly at Hct values o f 30% to 40%. This defect (but not that of thrombus formation) can be completely corrected by the addition of RBCs. The correction of the pl atelet adhesion defect by RBCs was specific for delta-SPD; it was not observed in either von Willebrand's disease or thrombasthenia. Studies performed on normal blood under conditions that could be expected to block any effect of ADP on adhesion and an analysis of the type of adh esion defect in delta-SPD suggest that ADP may be involved in the proc ess required for platelet spreading on the subendothelium. The correct ive effect of RBCs on platelet adhesion in delta-SPD appears to be che mical rather than physical in nature, possibly due to shear-induced re lease of RBC ADP or to other recently described properties of RBCs tha t enhance collagen-induced platelet interactions. (C) 1996 by The Amer ican Society of Hematology.