RESPONSE OF XENOBIOTIC METABOLIZING ENZYMES IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) TO ENDOSULFAN, DETECTED BY ENZYME-ACTIVITIES AND IMMUNOCHEMICAL METHODS

A single i.v. injection (75-mu-g/kg body weight) of the insecticide endosulfan was administered to gonadally immature rainbow trout (Oncorhynchus mykiss). Experiments were done with both technical and analytical grade endosulfan. In liver microsomes prepared from fish killed 24 h after administration, the cytochrome P-450-dependent monooxygenase activities of 7-ethoxyresorufin O-deethylase (EROD), aryl hydrocarbon hydroxylase (AHH), and aldrin epoxidase (AE) were measured. In addition, NADPH-cytochrome c reductase (NCCR) was analyzed, and the content of a specific cytochrome P-450 isozyme was determined with Western blotting and an enzyme-linked immunosorbent assay (ELISA) using rabbit anti-cod P-4501Al lgG. Technical grade endosulfan significantly induced EROD and AE to 160 and 144%, respectively, of the corresponding control values, while analytical grade endosulfan significantly increased only AE activity to 147% and tended to induce EROD to 162%. AHH and NCCR were not affected. The antibodies to cod P-4501A1 recognized a single protein band (M(r) = 58 Da) in the rainbow trout liver microsomes. The ELISA absorbances of this protein in the technical and analytical grade endosulfan treated fish were 151 and 138%, respectively, of the corresponding values in the controls. These results were supported by corresponding results from a 14 days study, where rainbow trout were exposed to technical grade endosulfan (8.3-mu-g/l water). In this study glutathione S-transferase (GST) activity towards 1,2-dichloro-4-nitrobenzene (DCNB) and 1-chloro-2,4-dinitrobenzene (CDNB) was also included, however, no effect on GST was observed.