Dependence of biological effects on chemical nature of /sup 111/In-labelled compounds

Subcellular localization of radiolabelled compounds is very much dependent on the chemical nature. If the radionuclide decays by electron-capture emitting several low energy electrons with very short ranges, the critical nature of the incorporation site and the energy density around it are important in determining the fate of the cell. Conventional MIRD dosimetry of incorporated radionuclides ignores this fact and assumes uniform deposition of energy, valid only when all the radiations emitted have ranges much greater than the cellular dimensions. Indium-111, an electron-capture radionuclide, was studied in the form of /sup 111/In-Oxine and /sup 111/In-Citrate for the biological effects in the mouse ovary which is very sensitive to radiation. The primary oocyte survival was investigated after injecting the compounds I.P. into the mice. It is found that /sup 111/In-Oxine is about 1.7 times more effective compared to /sup 111/In-Citrate. This is consistent with our earlier findings that /sup 111/In-Oxine, which is localized in the nucleus of the spermatogonial cells significantly higher than the Citrate, is 2.1 times more lethal in the mouse testis