Cholinesterase-Inhibiting Properties of Two Vinyl-Substituted Phosphates

1. Comparative cholinesterase-inhibiting activity of 2 new vinyl-substituted phosphates and parathion was studied in respect to their cumulative inhibitory properties, the rate of regeneration of the enzyme following single administration, and their inhibitory action in vitro. 2. While qualitatively resembling parathion in inhibitory action against cholinesterase, quantitatively the diethyl 2-chlorovinyl phosphate was found to be more active both in vitro and in vivo than parathion; and the dimethyl 1-carbomethoxy-l-propen-2-yl phosphate was less active in vivo. 3. By examination of the cumulative inhibitory properties of these 3 phosphates, the observation of others has been confirmed, that on increasing the dosage or duration of exposure to the cholinesterase inhibitor, remarkably low levels of enzyme activity can occur without fatal termination. 4. Erythrocyte cholinesterase was usually depressed to a greater extent than that of brain or plasma. There was some indication of a tolerance developing on the part of the “pseudo” cholinesterase with one of the compounds.