Enzyme effects and metabolism of fenitrothion in primary cell culture of the red swamp crayfish Procambarm clarkii

The toxic action of the organophosphate pesticide fenitrothion via metabolism to fenitrooxon was investigated in isolated mixed-population cells from the hepatopancreas of the non-target organism Procambarus clarkii. Glutathione- S -transferase (GST; substrate: 1-chloro-2,4-dinitrobenzene), 7-ethoxyresorufin O -deethylase (EROD) andacetylcholin esterase (AChE) specific activities (per mg protein) in 10000 g supernatants were 50–60% lower (GST, AChE), or markedly higher (EROD) in cells compared to whole tissues. However, EROD cell activity was similar to values recorded for whole tissue microsomes. Incubation (12 h) of isolated cells with up to 5 μM fenitrothion resulted in a marked inhibition (84%) of AChE activity, but an increase (50%) in GST activity ( p < 0.05). Fenitrothion (5 μM) was readily metabolised to fenitrooxon and 3-methyl-4-nitrophenol. The disappearance of fenitrothion but not the formation of the metabolites was inhibited by 100 μM α-naphthoflavone, indicating the possible involvement of multiple cytochrome P450 forms in the metabolism of fenitrothion.