Comparative effect of technical and commercial formulations of methamidophos on sperm quality and DNA integrity in mice.

Methamidophos (MET), widely used in developing countries, is a highly neurotoxic organophosphate pesticide that has been associated with male reproductive alterations. Commercial formulations of pesticides used by agricultural workers and urban sprayers are responsible for thousands of intoxications in developing countries and may not have the same effects as active pure ingredients. Therefore, we compared effects of MET technical (METt) and commercial (METc) grades on sperm quality and DNA integrity. Male mice were injected (intraperitoneal, i.p.) with METt or METc (3.75, 5, and 7 mg/kg bw/day/4 days) and sacrificed 24 h post-treatment. Sperm cells collected from epididymis-vas deferens were evaluated for quality parameters, DNA damage by the comet assay, and lipoperoxidation by malondialdehyde (MDA) production. Erythrocyte acetylcholinesterase (AChE) activity was evaluated by acetylthiocholine inhibition as an index of overall toxicity. A dose-dependent AChE inhibition was observed with both formulations. Sperm quality was decreased after treatment with both MET compounds, but the commercial formulation showed stronger effects; a similar profile was observed with the DNA damage, being METc more genotoxic. None MET formulation increased MDA, suggesting no peroxidative damage involved. In summary, the commercial formulation of MET was more reprotoxic and genotoxic than the active pure ingredient, highlighting that commercial formulations must be considered for more appropriate risk assessment of pesticide exposures.