Pesticide action: Different response of erythrocyte membrane acetylcholinesterase to inhibition by organophosphorus compounds under varied dietary conditions

Abstract The inhibitory effect of malathion in conjunction with maloxon or other derivatives on the activity of rat erythrocyte membrane-bound acetylcholinesterase has been investigated after feeding diets known to affect the lipid composition of the membrane. The inhibition of AchE by preincubation of membrane preparations with this organophosphorus compound, possibly with contaminants, differed with the diet: the curve was sigmoidal after supplementation with corn oil and hyperbolic after supplementation with lard. In the latter case the kinetics of the inhibition became sigmoidal by assaying in the presence of cortisol or isoproterenol or by previous solubilization of the enzyme. These results indicate that some organophosphorus compounds can differentiate conformational states of acetylcholinesterase present in the erythrocyte membrane.