Acute toxicological effects in rats treated with a mixture of commercially formulated products containing methyl parathion and permethrin

The study examined the interactions between a commercial formulation of methyl parathion (CF-MP) and a commercially formulated product of permethrin (CF-PMT) in male rats. The acute toxicity (LD50 values) and brain cholinesterase activity were investigated as toxicological endpoints. Results indicated that CF-MP modified the acute toxicity of CF-PMT. When animals were treated with a mixture, the addition of 380 mg/kg of CF-MP reduced the LD50 of CF-PMT by only 9.0%25; however, when rats received CF-MP at 464 mg/kg, the LD50 of CF-PMT was reduced by 37 %25 (P < 0.001). Also, CF-PMT decreased the CF-MP-induced inhibition of cholinesterase activity by 50%25 (P < 0.05). It was interesting to observe that xylene, which is the most abundant component in the vehicle of both formulations, had no effect on the CF-MP-induced inhibition of the cholinesterase activity. There was no relation between lethality and the inhibition of the brain cholinesterase activity in rats treated with mixtures containing CF-MP %2b CF-PMT or with either commercially formulated product alone. Considering the increased toxicity observed in rats treated with CF-PMT %2b CF-MP, it would be advisable to investigate further the interactions between both pesticides. © 1995 Academic Press, Inc.

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