The Effect of Cold on Platelets. I. Cold-induced Platelet Aggregation

Low temperatures induce platelet aggregation. This effect is greatest when chilled platelet-rich plasma (PRP) is stirred while it is warming or just after it has warmed. The stirring of chilled PRP at low temperature or after prolonged warming causes little aggregation. The extent of aggregation increases as the temperature at which the PRP is chilled is lowered, and as the time of chilling is lengthened. This phenomenon resembles ADP-induced aggregation in that the shape of the aggregation curves of both are similar and both are inhibited by the same compounds. In addition, both forms of aggregation require calcium. However, cold-induced aggregation is not mediated by ADP since this compound is not found in the supernatant of chilled PRP. Nor is the effect of cold on plasma proteins responsible for cold-induced aggregation since cold causes aggregation of platelets suspended in a nonprotein medium. The mechanism of this phenomenon may be similar to ADP-induced aggregation. Its clinical significance is that it may account for the deleterious effect of cold on the preparation and preservation of platelet concentrates.