Evaluation of Clastogenic/Aneugenic Damage Using the FISH Micronucleus Assay in Mice Exposed to Chromium (VI).

Abstract

Exposure to chromium (VI) [Cr(VI)] has been postulated to be associated with the induction of cancer. In vivo studies utilizing biomarkers of genotoxic damage could aid in elucidating the mechanisms underlying the genotoxic effects of Cr(VI) and their relationship with carcinogenesis. In this study, the origin (clastogenic and/or aneugenic damage) and kinetics of micronuclei (MN) induced by Cr(VI) were investigated. Hsd:ICR female mice were divided into groups of five individuals each. MN kinetics were measured in groups treated with 20 or 25 mg/kg CrO3 intraperitoneally using acridine orange-coated slides in peripheral blood obtained from the caudal vein 0, 12, 24, 36, 48, 60, and 72 h after treatment. Whereas identification of MN with centromeric DNA (MNK+) was measured at the dose of 20 mg/kg of CrO3, using fluorescence in situ hybridization (FISH) with a centromere-specific probe in peripheral blood obtained at 0, 12, and 48 h after treatment. Control groups were administered vehicle only. Total MN were quantified and the clastogenic/aneugenic effects of Cr(VI) were evaluated based on the proportion of MNK+ versus micronuclei without centromeric DNA (MNK-). There was a significant increase in MN frequencies beginning at 12 h in the Cr(VI)-treated groups demonstrating its genotoxicity. When calculating the MNK+ as a percentage of the total MN, the increase was significant beginning 12 h after treatment. The fact that the MNK+ and MNK- were observed at both evaluation times corroborates Cr(VI) as a genotoxic agent and demonstrates that both clastogenic and aneugenic damages are involved in the formation of MN.