The relationship between the age and density of circulating 51-Cr labelled platelets in the sub-human primate.

Change in the density of circulating platelets in monkeys was studied by using a method that removed greater than 90% of the platelet population from whole blood. These were labelled with 51-Cr and reinjected, having been protected by prostacyclin while in vitro. Platelets were separated into density subpopulations the following day by continuous linear gradients of polyvinyl pyrrolidone coated silica (Percoll) under conditions that approximated well to equilibrium centrifugation. The 51-Cr labelled platelets were then found to be distributed equally throughout all density subpopulations. When the same procedure was repeated at 5 days after re-injection an average of 5% of the density range increase in platelet density had occurred in the reinjected platelets compared to the circulating population (p less than 0.001). Lighter platelets may have a slightly shorter survival time than dense ones. Monkey platelet volume is log normally distributed.