Membrane-bound and soluble esterase activities in various hen brain regions after diisopropyl phosphorofluoridate and trichlorfon treatment.

Acetylcholinesterase, neurotoxic esterase, and nonspecific esterase activities were studied in subcellular fractions obtained from homogenates of forebrain, cerebellum, and brainstem areas of hen brain. The hens were given a single, oral dose (1.0 mg/kg of Dyflos (diisopropyl phosphorofluoridate) or 100 mg/kg of trichlorfon (dimethyl -2,2,2-trichloro-1-hydroxyethylphosphonate). The animals were killed 24 hr after dosing. The level of neurotoxic esterase and soluble nonspecific esterase activities were consistent from region to region; however, acetylcholinesterase activity among the brain regions varied significantly. Both organophosphorus compounds produced definite inhibition of acetylcholinesterase. The cerebellar acetylcholinesterase activity was the most susceptible to organophosphorus ester-induced inhibition. A marked inhibition of neurotoxic esterase (70-80%) was produced by diisopropyl phosphorofluoridate in all areas. Trichlorfon produced little or no inhibition of neurotoxic esterase (0-10%). Little variation in soluble nonspecific esterase activity (alpha -naphthyl acetate) was noted between the three brain regions studied. Both diisopropyl phosphorofluoridate and trichlorfon failed to significantly alter soluble nonspecific esterase activity among the brain regions.