Storage of Human Platelets in Liquid Nitrogen–Isotopic Studies

Concentrated platelet suspensions in 5% DMSO —5% PVP (MW 17,500) in plasma were frozen in sterile, slliconized glass vials at a rate of 1‐3C per minute to — 40C They were then immersed in liquid nitrogen and stored for a period of six to 12 months. After rapid thawing, platelets were labeled with 51Cr and injected into hematologically normal and ABO‐ and RH‐ compatible subjects. The radioactive recovery of frozen platelets, two hours after injection, was 11 per cent (3.9‐22). The recovery of fresh platelets labelled under the same conditions was 36 per cent (30‐50%). The platelet survival time was found to be four to six days for frozen platelets and six to nine days for fresh platelets. These results suggest that platelets frozen and stored in liquid nitrogen have a definite but reduced therapeutic efficiency. The method looks valuable for some blood banks.