During blood bank storage of platelet concentrates (PC), platelet actin is hydrolyzed into two fragments (SP-1, 29kd and SP-2, 27kD). To determine if calpain-induced proteolysis was responsible for degradation of actin, we analyzed cytoskeletal proteolysis in intact platelets obtained from units of PC stored under blood bank conditions for up to 10 days. PC were incubated with 0.9% NaC1 (control); calcium ionophore A23187 (calpain agonist); and leupeptin and E64d (calpain inhibitors). SDS-PAGE and immunoblotting was performed with probes for actin binding protein (ABP), talin, vinculin and glycoprotein Iib. Results showed that during blood bank preparation and storage, actin, ABP, talin and vinculin were degraded with concomitant generation of specific fragments over time. In contrast, glycoprotein Iib levels were unchanges during the storage period. Degradation of cytoskeletal proteins was enhanced by exposure of PC to A23187, and inhibited by incubation of PC with E64d. These results imply that calpain is involved in this degradative process and that cytoskeletal proteolysis may play a role in the development of the platelet storage lesion. Results of this study were presented at the annual meeting of the American Society for Hematology, December, 1991 and have been prepared for submission to BLOOD.
