Usefulness of (99m)Tc-d,l-HMPAO for estimation of GSH content in tumor tissues

To investigate whether [(99m)Tc]-hexamethyl propyleneamine oxime ([(99m)Tc]-HMPAO) is applicable for evaluating glutathione (GSH) localization in tumor, the difference of distribution between [(99m)Tc]-d,l- and meso-HMPAO was studied using a mouse tumor model. Biodistribution of [(99m)Tc]-d,l- or meso-HMPAO was studied in GSH-depleted and control Ehrlich tumor-bearing mice. GSH levels in tumors in GSH-depleted and control mice were measured in another set of mice. The uptake of [(99m)Tc]-d,l-HMPAO in tumor was significantly decreased by the diethyl maleate (DEM) treatment. On the other hand, the DEM treatment increased the accumulation of [(99m)Tc]-meso-HMPAO in tumor. Meanwhile, the content of GSH was lowest in tumor among the tissues tested and decreased in a manner similar to other tissues on preloading of DEM. [(99m)Tc]-d,l-HMPAO may be useful for estimating the GSH status in a certain tumor and thereby contribute to the diagnosis of anticancer therapy.