Response of xenobiotic metabolizing enzymes in rainbouw trout (Oncorhynchus mykiss) to endosulfan, detected by enzyme activities and immunochemical methods

Abstract

A single i.v. injection (75 μg/ 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 anticod P−4501 A1 IgG. 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−4501 A1 recognized a single protein band ( M 1 = 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 μg/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.