Survival of cooled platelets. In vivo biotinylated platelets were isolated and stored at 4°C (dotted line) or room temperature (solid line) for 2 hours without stirring and reinjected into a mouse. Blood samples were collected from time zero (<2 minutes, percentage of biotinylated platelets at time zero = 100) to 48 hours. The survival of platelets stored at room temperature and cooled platelets was compared for both wild-type (A) and P-selectin–deficient (B) mice. In both genotypes, cooling the platelets dramatically reduced their life span. No statistically significant differences between genotypes were detected; n = 6.