Parathion-methyl

Methyl parathion is an organophosphate insecticide. It is converted into an oxon-containing metabolite in vivo, similar to other organophosphate pesticides, that inhibits acetylcholinesterase. Methyl parathion is lethal to lab strains and field isolates of tobacco budworm larvae (LD₅₀s = 7 and 81.8-128.3 μg/g, respectively). It reduces the number of stink bugs (C. sayi) caught per 100 net sweeps when applied to alfalfa fields at a concentration of 0.4 pounds per acre. Methyl parathion increases sister chromatid exchange (SCE) in a concentration-dependent manner and induces cell cycle arrest at the M₁ phase in V79 cells at a concentration of 40 μg/ml. It is toxic to rats (LD₅₀ = 14 mg/kg).