An inexpensive, statically controlled cooling rate device comprising a cassette of metal plates and cardboard insulation in a plastic bag was used to freeze platelets in liquid nitrogen with glycerol-glucose as cryoprotectant. Depending on the thermocouple location, the cooling rate in the freezing bag varied between 22.1 DEG and 38.6 DEG C. per minute, averaging 33.6 DEG +/-1.1 DEG C. per minute at the center. The post-thaw recovery of platelets frozen with this device and reconstituted in plasma averaged 88.6+/-11.7 percent, compared to 86.1+/-9.9 percent for nonfrozen but identically processed platelets. [14C]Serotonin uptake after 0.5-hour incubation was 95.9+/-1.9 percent for fresh platelets in platelet-rich plasma, 92.7+/-4.4 percent for nonfrozen processed platelets, and 81.4+/-11.8 percent for frozen platelets, increasing to 85.9+/-7.7 percent after one-hour incubation.
