In vitro and in vivo behavior of 111In‐labelled platelets: An experimental study of healthy male volunteers

Abstract

The aim of this study was to obtain a critical evaluation of a simple method for labelling platelets with 111In-oxine. All experiments were carried out on healthy volunteers, 65 .+-. 7 (SD) % of the platelets in collected blood were labelled and reinjected. As compared to control experiments, only in response to a low final ADP concentration (1.0 .mu.mol/l) did 111In-labelled platelets show reduced in vitro aggregability. The mean platelet volume for 111In-labelled platelets was slightly lower than the mean platelet volume in whole blood. The results for initial platelet recovery and platelet mean life-span closely agreed with those of other studies in which considerably higher platelet extraction from whole blood was obtained. After injection, the splenic uptake and blood disappearance of 111In-labelled platelets followed a monoexponential function with almost identical rate constants. By compartmental analysis of the equilibration of platelets between blood and spleen, the splenic blood flow was estimated to be 4.8 .+-. 1.9 (SD) % of the total blood volume/min; the intrasplenic platelet transit time was 9.7 .+-. 1.6 (SD) min, and the exchangeable splenic platelet pool 31 .+-. 8 (SD) %. Highly significant relationships were present between the splenic blood flow and the splenic platelet pool size, as well as between the splenic blood flow and the initial platelet recovery. It is concluded that the requirements for adequate interpretation of platelet kinetics are well met with the present method for harvesting and labelling of platelets.