Protein changes occurring during storage of platelet concentrates

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Abstract
The changes in thrombocyte proteins during 22 degrees C storage of platelet concentrates (PC) were studied. To prepare a reference protein “map” of stored PC, platelet samples were taken on days 1, 7, and 21. The platelet proteins were separated by isoelectric focusing (first‐ dimension) followed by second‐dimension polyacrylamide gradient gel electrophoresis with sodium dodecylsulfate (2D). The silver‐stained gels were analyzed by computer to obtain a composite map of stored PC proteins. The pattern seen on day 1 changed during 7 days of storage, with 30 proteins increasing or decreasing in spot density. In general, the spot density for lower‐molecular‐weight proteins increased, whereas that for higher‐molecular‐weight proteins decreased. Membrane proteins of intact fresh and stored platelets were labeled with 3H using sodium metaperiodate‐[3H]NaBH4 and with 125I using lactoperoxidase‐H2O2. A comparison on the fluorographs of 2D gels of [3H]NaBH4‐labeled platelet proteins showed several protein spots in the stored Day 7 sample that had not been seen in the Day 1 sample. Similarly, for the autoradiographs, several 125I‐labeled proteins detected in Day 7 PC were not seen in the Day 1 samples. The results provide evidence that platelet proteins are altered during PC storage and that these changes involve platelet membrane proteins.