Comparison of 111In and 99mTC Labelled Monoclonal Antibodies in Normal Mice: Biodistribution Studies and Electrophoretic Analyses of Plasma Samples

Anti-melanoma monoclonal antibody (Mab) kits were obtained from Sorin, Italy. They were labeled with 111In and 99mTc. The labeling efficiencies determined by thin-layer chromatography (ITLC) were 97% and 99% for 111In-Mab and 99mTc - Mab, respectively. Each radiopharmaceutical was I.V. injected to 6 NMRI mice. Those mice injected with 111 In-Mab were sacrificed at 24 h and 48 h. The other 6 injected with 99m Tc-Mab were sacrificed at 6 h and 24 h. Some blood and organs were taken out for weighing and radioactivity assay. The maximum percent uptake per whole organ was obtained in the liver (5.65-0.09 % at 24 h and 6.14-0.10 % at 48 h). The maximum % uptake per g organ was obtained in kidneys (21.70-0.40 at h and 16.18-1.64 at 48 h). When 99mTc-Mab was used the maximum % uptake per whole organ (11.67-0.32 at 6 h, 5.01-0.07 at 24 h) and per g tissue (73.55-3.36 at 6 h, 27.73-0.94 at 24 h) were obtained in kidneys. Electrophoretic analyses of plasma samples indicated that 111In was transferred from Mab to plasma proteins, which explained the observed higher blood radioactivity levels compared to 99mTc-Mab.