BIOACCUMULATION, METABOLISM, AND BIOCHEMICAL EFFECTS OF THE ORGANOPHOSPHORUS PESTICIDE FENITROTHION IN PROCAMBARUS-CLARKII

Fenitrothion (O, O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioat e) is readily taken up from the water by the crayfish Procambarus clar kii. The bioconcentration factor, however, is lower than expected on t he basis of its octanol/water partition coefficient. The ability of P. clarkii to metabolize fenitrothion was evaluated in vitro by using 12 ,000-g supernatant or microsomal fractions isolated from hepatopancrea s and the results pointed out the existence of both oxidative and glut athione-mediated metabolism. Several biomarkers of exposure viz., the microsomal mixed-function oxygenase system, a phase II enzyme [glutath ione S-transferase], and acetylcholinesterase inhibition, were studied in organisms exposed to 20 mu g/L of fenitrothion for 48 h. Cytochrom e P450 content, NADPH cytochrome c(P450) reductase, and 7-ethoxyresoru fin O-deethylase activity showed significant induction the second day of treatment, whereas glutathione S-transferase activity appeared to b e unaffected. Acetylcholinesterase activity in the neuromuscular tissu e of P. clarkii was a good indicator of exposure to this compound.