Antigenotoxic properties of selenium compounds on potassium dichromate and hydrogen peroxide.

Selenium is an environmental metal that occurs ubiquitously and is produced throughout the world for various industrial activities. Selenium has been reported to have anticarcinogenic and preventive effects in clinical and epidemiological studies. Selenium supplements can inhibit chemically-induced tumours. From the viewpoint of genotoxicity, selenium has not been adequately studied and an IARC review concluded that there were not sufficient data to consider it a carcinogen for man. In contrast, hexavalent chromium is classified as a known respiratory carcinogen producing DNA damage through free oxygen radicals. In the present study, a collaborative study has been carried out to evaluate the genotoxicity of selenium compounds and their possible interactions with potassium dichromate and hydrogen peroxide. Thus, in laboratory 1 (U.K.), the genotoxic effects of three selenium compounds were examined. Sodium selenate, sodium selenite, and selenous acid were investigated in the Ames test using strain TA102 and in the Comet assay using human lymphocytes, and also investigated for their interaction with potassium dichromate. In the Ames test, it was shown that potassium dichromate produced a highly mutagenic response, whilst the three selenium compounds did not. In combination, sodium selenate reduced the genotoxicity of potassium dichromate, but sodium selenite and selenous acid had no effect. In the Comet assay, potassium dichromate induced DNA damage, but so did the selenium compounds. In combination with potassium dichromate, however, only sodium selenate reduced its effect, whereas sodium selenite and selenous acid exacerbated DNA damage. In laboratory 2 (Spain), in the TK6 lymphoblastoid cell line, the Comet assay showed that sodium selenite was non-genotoxic, while potassium dichromate and hydrogen peroxide induced DNA damage. It was also shown that sodium selenite did not decrease the genotoxicity of potassium dichromate or hydrogen peroxide when administered as a pre-treatment or at the same time, or when potassium dichromate and sodium selenite treatments were for different time periods. Thus, only sodium selenate has shown antigenotoxic properties against potassium dichromate in the Ames test and in human lymphocytes in the Comet assay.