Hydrolytic and metabolic products of acephate in water and mouse liver

Acephate was incubated in distilled water of three different pH's at 37 degrees C for 7 days. Three hydrolytic products were formed: methamidophos, O,S-dimethyl phosphorothiolate (DMPT), and O-methylacetyl phosphoramidothiolate (OMPT). A single dose of acephate was also fed to mice, and their livers were excised and analyzed for metabolic products up to 30 hours. Three products were detected: methamidophos, DMPT, and S-methylacetyl phosphoramidothiolate (SMPT). The anticholinesterase properties of acephate, methamidophos, DMPT, SMPT, and OMPT were determined. Only acephate and methamidophos had measurable inhibitory effects on the mouse erythrocyte enzyme, methamidophos being about ten times more effective than acephate. The amount of methamidophos formed in the water and mouse liver was too low to have any direct effect on the toxicity of acephate. Acephate toxicity to aquatic insects would depend on its persistence in water, its uptake by the insects, its conversion to methamidophos, and the combined inhibitory effect of acephate and methamidophos on the cholinesterase enzyme. The toxicity of acephate to mammals would depend on the direct anticholinesterase effect of the chemical and to a small extent on methamidophos.