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
