AVIAN PLASMA CARBOXYLESTERASE ACTIVITY AS A POTENTIAL BIOMARKER OF ORGANOPHOSPHATE PESTICIDE EXPOSURE

Abstract

Plasma cholinesterase (ChE) and carboxylesterase (CaE) activities were measured in pigeons (Columba hvia), captive and wild American kestrels (Falco sparveius), red-tailed hawks (Buteo jamaicensis), Swainson's hawks (Buteo swainsoni), Cooper's hawks (Accipiter cooperit), and red-shouldered hawks (Buteo lineatus). The effect of organophosphate (OP) insecticides on pigeon ChE and CaE activities was determined. Pigeon plasma CaE activity showed distinct groups averaging 12.4 and 138 nmol/min/ml plasma. The CaE activity for raptors was less than 20 nmol/min/ml plasma. Both ChE and CaE activities were inhibited by 0.4 mg/kg ethyl parathion, but CaE activity was not inhibited by 10 mg/kg methidathion. There was no difference in the blood ChE activities of pigeons with low or high blood CaE after treatment with parathion. In general, CaE activity was less severely depressed and recovery was less predictable than was ChE activity.