Aggregation response of human platelets stored at 22 C as platelet-rich plasma. 
The aggregating response of human platelets stored at 22 C for 72 hours has been studied.  Platelets were stored as platelet-rich plasma in order to maintain the plasma pH essentially constant.  The response to ADP and collagen decreased with time, but the decrease was less with relatively high concentrations of the aggregating agents.  The response to the ionophore A23187 was essentially unaltered during the storage period.  Synergistic aggregation with combinations of ADP, collagen and ionophore A23187 was observed with platelets stored for 72 hours under conditions where singly each of the stimuli caused little or no effect.  Stored platelets underwent reversible aggregation over a wide range of ADP concentrations but irreversible aggregation was observed in the presence of nonaggregating concentrations of collagen or ionophore A23187.  The inhibition of aggregation by PGE1 or cyclic AMP was facilitated as a result of storage.  It is suggested that the decreased response toward ADP and collagen reflects a reduced ability on the part of the platelets to mobilize calcium.