Comparison of Oxine and Tropolone Methods for Labeling Human Platelets with Indium-111

The effect of the chelates oxine and tropolone, used to label platelets, on the kinetics of indium-111-({sup 111}In) labeled platelets was studied in twelve normal human subjects. Autologous platelets were labeled either in saline with {sup 111}In-oxine or in plasma with {sup 111}In-tropolone. Mean platelet lifespan was estimated by fitting the disappearance curve of platelets from the circulation to the multiple hit and other mathematical models. The in vivo distribution of platelets was quantitatively imaged with a scintillation camera. The in vivo recovery of {sup 111}In-oxine and {sup 111}In-tropolone did not differ, and the mean platelet lifespan was also similar ({sup 111}In-oxine: 230 +/- 29 hr; {sup 111}In-tropolone: 226 +/- 13 hr). At equilibrium (90 min after reinjection of labeled platelets) and at the end of platelet lifespan, {sup 111}In-oxine and {sup 111}In-tropolone radioactivities in the spleen and liver were similar. These results demonstrate that the results of kinetics measured with {sup 111}In-oxine or {sup 111}In-tropolone do not differ significantly.