EFFECT OF AMBIENT STORAGE ON PLATELET MEMBRANE-STRUCTURE AND RESPONSE TO THROMBIN

Blood platelets rapidly lose hemostatic function during in vitro storage at room temperature. In view of recent studies implicating platelet surface proteins in some aspects of platelet function, we have examined the effect of platelet storage on membrane structure and function. Platelets obtained from a single donor by double plateletpheresis were stored for seven days at 22 C with constant agitation. On succeeding days, platelets were removed and analyzed for membrane surface structure determined by iodination of membrane surface proteins, membrane function determined by serotonin uptake and equilibrium binding of thrombin to surface receptors, and platelet (unction determined by serotonin release and platelet aggregation in response to thrombin. The earliest changes in membrane surface structure were observed within 48 hours and consisted of decreased iodination of membrane surface proteins, and increased iodination of membrane proteins with estimated molecular weights of 260,000, 240,000, and 84,000. No changes were observed in the overall protein composition of the platelet, but changes in membrane function were observed. Relative uptake of serotonin decreased from 89 to 37 per cent and appeared to occur in parallel with the changes in membrane surface proteins. Changes in thrombin binding, on the other hand, were progressive throughout the storage period. The number of molecules of thrombin bound with high affinity decrease from 1,040 to 520 per platelet while the number of molecules bound with low affinity decreased from 103,600 to 4,500. No persistent alterations were observed in the affinity of thrombin for its receptors. Thrombin‐induced platelet aggregation and release of serotonin decreased in parallel with the changes in thrombin binding. 1979 AABB