Kinetics, distribution, and sites of destruction of canine blood platelets with In-111 oxine

In five normal dogs we have studied the survival, tissue distribution, and fate of autologous platelets labeled with indium-111 oxine. The methods include blood sampling, computer-assisted scintigraphy, and whole-body profile scanning. Mean In-111-platelet recovery in the circulation was 45 +- 22.5 (s.d.) and survival 124.6 +- 10.5 h. Platelet survival curves fitted a linear function best. Initially platelets pooled rapidly in the spleen with a single exponential function, and at zero-time equilibrium (35 +- 4)% of the injected In-111 was located in this organ. Early hepatic uptake was also significant, and constituted (20 +- 4)% of total-body radioactivity. As labeled platelets disappeared from the circulation, In-111 activity in the spleen increased progressively and linearly to reach (59 +- 9)% of the body activity at 120 h. Hepatic radioactivity decreased with time but to a lesser extent than that of the heart. The results indicate that in the dog the major site of destruction of platelets is the spleen, with the liver playing a less important role