The recommended and commonly used methods for the isolation of platelets from whole blood do not harvest a representative platelet population. There is evidence that these methods may result in the loss of a functionally more active platelet subpopulation. We describe a method whereby a completely representative population of platelets was isolated from the whole blood of 28 normal human volunteers by repeated washing of platelets from the red-cell layer. The harvesting efficiency was 98.3%±2.8%. The platelets were labelled with 111In-oxine in a saline milieu with a labelling efficiency of 86.4%±6.8%. The disappearance of reinjected labelled autologous platelets from the circulation was almost linear, and the mean platelet survival was estimated to be 224±23 h. At equilibrium, 61%±12% of the labelled platelets were recovered from the circulation. The in vivo distribution at equilibrium and the sites of sequestration of the senescent labelled platelets were determined by geometric-mean whole-body quantification in six of the volunteers. This improved method permits accurate quantification of organ 111In radioactivity. Following reinjection, the labelled platelets pooled in the spleen and the accumulated activity can be presented by a single exponential function. At equilibrium, 31.1%±6.1% and 9.6%±1.2% of the platelets were in the spleen and liver, respectively. Splenic and hepatic radioactivity increased significantly with time, and at the end of the platelet life span, 35.6%±9.7% and 28.7%±8.3% of the labelled platelets were sequestrated in these organs, respectively. The 30.3%±7.8% remaining platelets were probably sequestrated mainly in the reticuloendothelial component of the bone marrow and other tissues. These techniques of platelet labelling and measurement of the in vivo distribution of 111In-labelled platelets are relatively simply and accurate methods for the study of platelet kinetics in man.

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   |clé=     ISTEX:259_1985_Article_BF00252745.pdf
   |texte=   An improved method for the quantification of the in vivo kinetics of a representative population of 111In-labelled human platelets
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