Abstract
o-Nitrophenyl butyrate was used as a substrate for measuring blood esterase activity. Human serum esterase was inhibited almost completely by 10-6 M of TEPP, 10-7 M of Phosdrin and 10-4 M of Eserin. Mouse serum esterase was inhibited to the extent of 80 and 98 % in the same concentration of Eserin and TEPP respectively. On the other hand, inhibition of rat and rabbit esterases by above inhibitors are markedly slight, particulary that of rabbit is inhibited only less than 5 % by Eserin treatment. This is probably caused by high content of A-esterase in the serum. It was recognized that human and pig serum are most suitable as the enzyme sources for the analysis of organophosphorous insecticides remaining in plants by the choline esterase inhibition method.
