Dl-α-tocopherol enhances the herbicide 1,1'-dimetyl-4,4'-bipyridium dichloride (paraquat, PQ) genotoxicity in cultured anuran leukocytes.

This cytogenetic and pharmacological study attempts to clarify genotoxicity-enhancement-effect of dl-α-tocopherol (one form of vitamin E) in combination with the herbicide 1,1'-dimetyl-4,4'-bipyridium dichloride (paraquat, PQ) on cultured anuran leukocytes using the superoxide dismutase-mimic Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin (Mn(III)TMpyP), the hydrogen peroxide-scavenger catalase and the electron donor nicotinamide adenine dinucleotido phosphate (NADPH). PQ only was found to induce structural chromosomal damage in cultured anuran leukocytes in a dose-dependent manner. PQ plus NADPH, which served as positive control, enhanced the genotoxic effect of PQ. Dl-α-tocopherol only did not induce any structural chromosomal damage in the leukocytes. PQ plus dl-α-tocopherol, however, enhanced the genotoxic effect of PQ. PQ plus Mn(III)TMpyP, PQ plus catalase and PQ plus Mn(III)TMpyP plus catalse suppressed the genotoxic effect of PQ. Furthermore, PQ plus dl-α-tocopherol-enhanced chromosomal damage was also inhibited by Mn(III)TMpyP plus catalase. These results suggest that dl-α-tocopherol in combination with PQ functions as an electron donor to PQ.