Bioaccumulation, metabolism, and biochemical effects of the organophosphorus pesticide fenitrothion inProcambarus clarkii

Fenitrothion (O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate) is readily taken up from the water by the crayfish Procambarus clarkii. The bioconcentration factor, however, is lower than expected on the 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 hepatopancreas and the results pointed out the existence of both oxidative and glutathione-mediated metabolism. Several biomarkers of exposure viz., the microsomal mixed-function oxygenase system, a phase II enzyme [glutathione S-transferase], and acetylcholinesterase inhibition, were studied in organisms exposed to 20 μg/L of fenitrothion for 48 h. Cytochrome P450 content, NADPH cytochrome c(P450) reductase, and 7-ethoxyresorufin O-deethylase activity showed significant induction the second day of treatment, whereas glutathione S-transferase activity appeared to be unaffected. Acetylcholinesterase activity in the neuromuscular tissue of P. clarkii was a good indicator of exposure to this compound.