Correlation between organophosphate poisoning, acetylcholinesterase inhibition, and increased cyclic GMP levels in malathion-treated insects

Abstract

Organophosphate poisoning with malathion caused large increases (up to 125 and 440%, respectively) in the level of cyclic GMP in larvae of Mamestra configurata Wlk. and in the fly Sarcophaga bullata Parker. Cyclic AMP was little affected. The malathion-induced increase in cyclic GMP was time and dose dependent. Time-course studies with the head and thorax of S. bullata demonstrated that the increase in cyclic GMP level occurred precipitously after a lag period of about 1 h, during which time the activity of acetylcholinesterase (EC 3.1.1.7) was progressively inhibited. The abrupt increase in cyclic GMP began when acetylcholinesterase activity had been inhibited to a sufficient extent to permit accumulation of acetylcholine. It is suggested that the accumulation of acetylcholine in the malathion-poisoned insects caused cyclic GMP levels to rise.Cyclic GMP may have a role in cholinergic transmission in normally functioning insect neural tissue. Increased levels of cyclic GMP induced by organophosphate and organochlorine (Bodnaryk, R. P. (1976) Can. J. Biochem. 54, 957–962) insecticides appear to be a vital and previously unrecognized biochemical lesion in insects poisoned by these compounds.