Investigation on the Genotoxic Effects of Long-Term Administration of Sodium Arsenite in Bone Marrow and Testicular Cells In Vivo Using the Comet Assay

Abstract

The main source of environmental arsenic exposure in most populations is drinking water in which inorganic forms of arsenic predominate. The single-cell gel electrophoresis technique (the comet assay) measures DNA damage, including double-strand and single-strand breaks, in somatic cells after a variety of genotoxic insults. We have used this method to measure damage to cellular DNA in the bone marrow and testicular cells of mice using the alkaline comet assay for the former and neutral comet assay for the latter. Swiss albino male mice were exposed to sodium arsenite in drinking water at concentrations of 10, 50,100, and 200 mg/l for a period of three months. Concurrently, negative and positive control sets were maintained. The negative control animals were given distilled water as drinking water for the same period of treatment while the animals in positive control sets were either given single or multiple injections of EMS (100 mg/kg body weight) according to the tissue sampled. Following long-term exposure, there was a significant dose-dependent reduction in the size and weight of testes. The comet parameters of DNA, such as tail length (microm), % of DNA in tail, and Olive tail moment (arbitrary units) were increased in both bone marrow and testicular cells due to arsenic-induced DNA strand breaks. A positive dose response relationship was noted. The magnitude of DNA strand break was more pronounced in the bone marrow cells than in the testicular cells. The minimum effective concentrations for inducing DNA damage in bone marrow cells and testicular cells were 10 mg/l and 50 mg/l, respectively. The results of the study indicate that arsenic in drinking water is genotoxic in mice and the comet assay can be used for examining DNA damage in testicular cells as a parameter for evaluating male reproductive toxicity.