Activation of in vivo metabolism of malathion in male Tilapia nilotica

Male Tilapia nilotica from the Nile river, Egypt were exposed to concentrations of 0, 200, 500 or 1000 ug malathion per litre for up to 7 d. Half of the fish were pre-injected with phenobarbital. Malathion uptake and accumulation generally increased with increasing malathion concentration and exposure time. Malathion accumulation in the intestine, liver, muscle and gills was determined. The lowest values were observed in the gills. High levels of metabolites were found in the intestine and gills. Injection with phenobarbital, a mixed function oxidase activator (MFO), resulted in active uptake of malathion. The gills and intestine of induced MFO activated fish accumulated relatively high levels of malathion metabolites. The metabolite ratios were used to elucidate the metabolic pathways of malathion in T. nilotica.