Interaction of dichlorvos and anticholinesterases on the in vitro inhibition of human blood cholinesterases

Abstract

The inhibition of cholinesterase activity by dichlorvos and other anticholinesterases was tested manometrically using human red blood cells (RBC) and plasma as the enzyme sources with acetylcholine as the substrate. Using log probit plots the I50 values were calculated for all compounds. Combinations of dichlorvos with the agents carbaryl, crotoxyphos, malathion, malaoxon, parathion, paraoxon, mevinphos, dimecron, physostigmine, and trichlorofon produced either no change or less inhibition of cholinesterase activities than the calculated sum of the individual inhibition. Combinations of chlorpromazine with dichlorvos resulted in a greater inhibition of RBC cholinesterase activity than expected from the calculated summed individual inhibitions and less inhibition with the combination compared to the calculated summed individual inhibitions when plasma was used. There was the same inhibition with the combination of chlorpromazine and dichlorvos compared to the summed individual inhibitions using purified bovine erythrocyte acetylcholinesterase.