Inhibition of cholinesterase (ChE) activity was examined by experiments on enzyme activity of ChE of rat administered intraperitoneally chlorpyrifos and enzyme kinetic study of ChE in plasma. Plasma ChE activity was inhibited more highly than erythrocyte ChE activity in rat 12 hrs after administration. Plasma ChE activity was recovered 1 month after administration but erythrocyte ChE activity was not recovered. No difference between frontal cortex and striatum ChE activity was recognized. Changes in brain ChE activity was similar to those in erythrocyte ChE activity. PAM affected the inhibition of ChE activity by chlorpyrifos on 3 hrs after administration but other ChE activities were not.
Uncompetitive inhibition between chlorpyrifos and ChE was proved by Lineweaver-Burk plots.
Inhibition of ChE isoenzyme was found on bands 4 and 7 by electrophoresis. These results suggest that plasma ChE was effective for exposure monitoring and erythrocyte ChE was effective for effect monitoring.