Air Containing Ions Generated by Electric Discharge Has No Potential to Induce DNA Damage in Lung Cells in Rats and Mice

Abstract

The comet assay is widely used as an in vivo/in vitro genotoxicity test to detect initial DNA damage in a single cell. Air containing ions generated by electric discharge was examined in lung comet assays in rats and mice. Using whole-body inhalation, the animals were continuously exposed to the ionized air (abbreviated as IONA) for 48 h at the concentrations range 100−700×10⁴ ions/cm³. Lung cell samples were prepared by mincing, and blood cells were also sampled and diluted with mincing buffer to confirm the results obtained with lung cells. Slide preparation and electrophoresis for the comet assay were conducted in accordance with the standard protocol (Version 14.2) provided by the Validation Management Team of the “International Validation Study of In Vivo Alkaline Comet Assay” controlled by the Japanese Center for the Validation of Alternative Methods (JaCVAM). Results of the lung comet assays in both rats and mice showed that the IONA exposure induced no significant differences in tail migration (tail length) or DNA-percentage in tail. In contrast, ethyl methanesulfonate used as the positive control gave clear positive responses in the assays. In the IONA-exposed groups, no abnormal changes were noted in clinical observations or body weight for rats or mice. Additionally, no IONA exposure-related abnormalities were detected in histopathological examinations in either species. Taken together, these results indicate that IONA has no potential to induce DNA damage in the lungs and has no effect on the general health conditions of animals, body weight or histopathology in the lungs under the conditions employed in this study.