Kinetics of In-111-Platelets in the Baboon: II. In Vivo Distribution and Sites of Sequestration

Summary

The kinetics and sites of sequestration of a fully representative population of In-111-platelets were determined in 11 baboons. The in vivo method of quantification with computer assisted scintillation camera image analysis was validated by sacrificing 5 baboons and measuring and comparing the distribution of organ radioactivity. Recovery of platelets in the circulation was 87% ±7, and their mean survival time was 147 hr± 15. The mean splenic platelet pool was 16.0% ± 1.9. At equilibrium 15.8% ± 2.9 of the In-111-platelets were in the hepatic blood pool. Senescent platelets were destroyed in the reticulo-endothelial system. The major sites of sequestration were: liver (37.6% ±6.0), and the spleen (23.3% ±4.6). The bone marrow sequestrated 14.4% ± 1.7 of the labelled platelets, and 15.5% ±4.0 were present in various other tissues. We conclude that the in vivo method of In-111- quantification is accurate. Senescent platelets are mainly sequestrated in the reticuloendothelial tissue, with the liver, spleen and the bone marrow important sites of sequestration.

Keywords

Platelets kinetics - Primates - Sites of platelet sequestration - Indium-111 - Indium-111-labelled platelets

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