Platelet labeling with Ga-67 (Ga-67-oxine, -tropolone, -MPO)

Ga-68-labeled platelets could be useful for positron emission tomographic studies (PET) of thrombosis and / or atherosclerosis. In order to identify the best chelate for radiolabeling of platelets with Ga-68, we investigated the platelet uptake of Ga-67 (Ga-67-oxine, -tropolone, and -MPO). The influence of platelet-density (1.10(7)-1.10(9)), temperature (4 degrees, 22 degrees and 37 degrees C) and time (1, 5, 10, 20, 30 minutes) of incubation and the amount of radioactivity (0.01-1 mu Ci/ml), were analysed. The platelet uptake of Ga-67-oxine and -tropolone is very low (5%). The platelet uptake of Ga-67-MPO on the other hand increases with density of platelets (highest at 10(9) platelets/ml). The labeling efficiency is also dependent on both temperature (37 degrees C>22 degrees C>4 degrees C) and time of incubation (highest at 30 minutes), but independent on the amount of radioactivity. Our data provide information about the Ga-67 (Ga-67-oxine, -tropolone, and -MPO) uptake and mechanism and may have some relevance for the clinical use of Ga-68-labeled platelets for PET studies.