The organophosphorus compounds constitute one major group of insecticides, and a certain portion thereof may be transported to the aquatic environment resulting either from the actual use on paddy fields or from unavoidable transmittance to waterways. However, possibly because of its relatively shorter persistence, the translocation and transformation of organophosphorus compounds in the aquatic environment has not been extensively investigated as compared with more persistent organοchlorine compounds.Fenitrothion, O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate, is widely used for the control of paddy field insects and forest protection in several countries, and since it is rather highly toxic to some aquatic organisms (LC 50 after 48hr exposure, 1.28 ppm for rainbow trout, 2.72 ppm for bluegill, 4.4 ppm for carp, LC 50 after 3 hr exposure, 0.0092 ppm for daphnia and no-effect dosage after 4 week exposure, 0.02 ppm for carp) (1, 2), the knowledge on degradation and metabolism of the compound in the aquatic environment is important for assessing short-term and long-term impacts on the non-target aquatic organisms.In this article metabolism and bioaccumulation of fenitro thion in several aquatic species are dealt with under laboratory conditions.
Metabolism in vitroTo acquire information on the intrinsic metabolic activity of aquatic organisms, liver of carp (Cyprinus carpio Linnaeus), rainbow trout (Salmo gairdneri) and freshwater snail (Cipangopaludina japonica Martens) was dissected out, homogenized in 0.1M phosphate buffer, pH 7.5, and centrifuged at 105,000 g for 60 min to obtain the microsome-equivalent (described as the microsomal fraction hereafter) fraction. The protein content of microsomal and sub microsomal (supernatant fractions by Lowry's method, micro somal P-450 content (3), activity of aniline hydroxylase (4) and aminopyrine N-demethylase (_5) were determined. Table I shows the results which reveal that the drug-0-8412-0489-6/79/47-099-003$05.00/0