Evaluation of Deoxyribonucleic Acid Toxicity Induced by the Radiopharmaceutical (99m)Technetium-Methylenediphosphonic Acid and by Stannous Chloride in Wistar Rats

Radiopharmaceuticals are employed in patient diagnostics and disease treatments. Concerning the diagnosis aspect, technetium-99m ((99m)Tc) is utilized to label radiopharmaceuticals for single photon computed emission tomography (SPECT) due to its physical and chemical characteristics. (99m)Tc fixation on pharmaceuticals depends on a reducing agent, stannous chloride (SnCl(2)) being the most widely-utilized. The genotoxic, clastogenic and anegenic properties of the (99m)Tc-MDP(methylene diphosphonate used for bone SPECT) and SnCl(2) were evaluated in Wistar rat blood cells using the Comet assay and micronucleus test. The experimental approach was to endovenously administer NaCl 0.9% (negative control), cyclophosphamide 50 mg/kg b.w. (positive control), SnCl(2) 500 μg/mL or (99m)Tc-MDP to animals and blood samples taken immediately before the injection, 3, and 24 h after (in the Comet assay) and 36 h after, for micronucleus test. The data showed that both SnCl(2) and (99m)Tc-MDP-induced deoxyribonucleic acid (DNA) strand breaks in rat total blood cells, suggesting genotoxic potential. The (99m)Tc-MDP was not able to induce a significant DNA strand breaks increase in in vivo assays. Taken together, the data presented here points to the formation of a complex between SnCl(2) in the radiopharmaceutical (99m)Tc-MDP, responsible for the decrease in cell damage, compared to both isolated chemical agents. These findings are important for the practice of nuclear medicine.