Effect of repeated oral administration of quinalphos on blood esterases in Bubalus bubalis

The effect of quinalphos on blood esterases was investigated in male buffalo calves after daily oral doses of 0.7, 1.4 and 2.1 mg/kg body weight for 28 consecutive days. Quinalphos markedly inactivated serum carboxylesterase (69-90%) and plasma cholinesterase activity (75-88%). Esterase activities in animals receiving 0.7 mg/kg/day of quinalphos approached normal levels 14 days after the termination of its ingestion. The results suggest that quinalphos is an effective inhibitor of blood esterases in vivo and its repeated exposure to buffaloes may impair detoxification of organophosphorus insecticides that are mainly biodegraded by carboxylesterase enzyme.