Kinetics of In-111-platelets in the baboon: I. Isolation and labelling of a viable and representative platelet population.

A fully representative and viable platelet population was isolated from the blood of 15 baboons by a multiwash procedure, and labelled with In-111-oxine. The recovery of the total platelet population in the circulation was 85% +/- 9. Mean platelet life span was 146 hr +/- 13. Correcting for plasma radioactivity (always less than 3.5%) did not significantly affect the estimate of platelet life span (145 hr +/- 16) or recovery (85% +/- 12). Platelet survival estimates, repeated at different times, were reproducible. In 5 baboons, platelets were also harvested by a single step differential centrifugation. The mean life span of a representative platelet population was significantly longer than that of platelets harvested by a single step. Recovery values of the representative and non-representative population were similar. We conclude that it may be important to harvest and label a fully representative platelet population for kinetic studies. The proposed method is simple and reproducible, and may be applied in studies in humans.