Preservation of Viable Platelets by Freezing. Effect of Plastic Containers

The in vitro biphasic reaction of platelets to hypotonic stress measured in a spectrophotometer (reversal reaction) was used as an indicator of platelet integrity in a series of experiments on preservation of human platelets by freezing. Following these results as a guideline, human platelets were cooled at 1° per min to −35° using 5% DMSO in plasma as the cryoprotective agent. Addition and removal of the DMSO was done very gradually to minimize osmotic stress. Survival studies after labeling with radioactive sodium chromate demonstrated nearly normal viability of the frozen-thawed platelets. Platelets frozen in polyvinyl chloride bags had lower recovery values than platelets frozen in polyolefin bags. Correlation between in vivo viability of the frozen platelets and values of in vitro reversal reaction was highly significant further suggesting that this practical in vitro test may be a valid indicator of platelet viability in experiments of this type.