Cytotoxic and genotoxic effects induced by stannous chloride associated to nuclear medicine kits

Abstract At present, more than 75% of routine nuclear medicine diagnostic procedures use technetium-99m ( 99m Tc). The binding between 99m Tc and the drug to obtain the radiopharmaceutical needs a reducing agent, with stannous chloride (SnCl 2 ) being one of the most used. There are controversies about the cytotoxic, genotoxic and mutagenic effects of SnCl 2 in the literature. Thus, the approaches below were used to better understand the biological effects of this salt and its association in nuclear medicine kits [methylenediphosphonate (MDP) bone scintigraphy and diethylenetriaminepentaacetic acid (DTPA) kidney and brain scintigraphy]: (i) bacterial inactivation experiments; (ii) agarose gel electrophoresis of supercoiled and linear plasmid DNA and (iii) bacterial transformation assay. The Escherichia coli strains used here were AB1157 (wild type) and BW9091 ( xthA mutant). Data obtained showed that both MDP and SnCl 2 presented a high toxicity, but this was not observed when they were assayed together in the kit, thereby displaying a mutual protect effect. DTPA salt showed a moderate toxicity, and once more, the DTPA kit provided protection, compared to the SnCl 2 effect alone. The results suggest a possible complex formation, either MDP-SnCl 2 or DTPA-SnCl 2 , originating an atoxic compound. On the other hand, SnCl 2 -induced cell inactivation and the decrease in bacterial transformation generated by DTPA found in XthA mutant strain suggest that the lack of this enzyme could be responsible for the effects observed, being necessary to induce DNA damage repair.