Platelet Tagging with Tritium Labeled Diisopropylfluorophosphate

A method is described for tagging platelets either in vitro or in vivo with tritium labeled diisopropylfluorophosphate, burning the tagged platelets by a modification of the Schöniger combustion technic and counting the resultant tritiated water by liquid scintillation counting. The curve of in vitro uptake of DFP-H3 by the platelet suggests that more than one protein in or on the platelet takes up the DFP. However, a saturation point is reached, as indicated by a plateau in the uptake curve. The survival curve of in vivo tagged platelets in five normal dogs is exponential with a half-life of 2.4 days. This can be explained by random destruction of platelets or by elution of the tag. The DFP-H3 tag has several advantages over the DFP32 tag. Either smaller doses of DFP or higher levels of radioactivity or both may be achieved with this technic.