Preservation of the Clot‐Retracting Activity of Platelets by Freezing in Dimethylsulfoxide and Plasma

Abstract

The clot retracting activity (CRA) of frozen platelets was studied as the in vitro test best representing the functional "integrity" of platelets. Dimethylsulfoxide as an additive in the preservation by freezing of platelets acts most effectively in the presence of plasma. Freezing of the platelets in a suspending medium consisting of 50 per cent plasma in saline with 15 per cent DMS, resulted in a 10 to 15 per cent loss over the fresh control CRA values. Freezing rates ranging from 3 C. to 30 C. per minute can be used without modifying the final result. Storage in liquid nitrogen for 38 days resulted in a 34 per cent CRA reduction over the frozen but not stored platelets. These results seem to justify trials of the in ~i v o survival of platelets preserved by these methods.