Cytochrome P-450 Monooxygenase Complex And Glutathione-Stransferase In Sarotherodon Melano Theron As Biomarkers Of Pollution.

Abstract Samples of Sarotherodon melanotheron obtained from water bodies of different pollution histories, that is, a site on the Volta lake near Ada, the Fosu lagoon at Cape Coast and aquaria containing the herbicide, 'Roundup', were used to investigate induction of hepatic cytochrome P-450 monooxygenase enzyme system (CYP) and glutathione-stransferase (GST) in response to pollutants. Total microsomal protein concentration was determined by the FolinLowry method. The activity of NADPH cytochrome P-450 reductase, a component of monooxygenase enzyme system, was measured, using reduction of exogenous cytochrome C. Another component, cytochrome P-450, was measured using CO-difference spectrum. The overall monooxygenase activity was determined using 7-ethoxyresorufin-0- deethylase (EROD) and 7-pentoxyresorufin-O-depentylase (PROD) assays, which indicated specifically, the induction of cytochrome P-4501A and P-4502B isoenzymes respectively. Glutathione-s-transferase activity was measured using l-chloro-2,4-dinitrobenzene as the substrate. The results for all the biochemical parameters measured, indicated that the levels of those of the fish from Fosu lagoon were excessively higher than the values recorded for fish from Volta lake and the aquaria, indicating a relatively higher pollution level in the Fosu lagoon. For the CYP the levels measured for both fish from ix the Fosu lagoon and the aquaria were almost similar, indicating higher induction of CYP by 'Roundup' . For the EROD and PROD determinations for the monooxygenase system, activities were detected in livers of fish from Fosu lagoon and the Volta lake. No such activities were detected in fish exposed to 'Roundup', even though CYP induction was high and these monooxygenase enzyme activities were found prior to herbicide exposure. The activity of EROD was 3.5 fold higher than that of PROD, indicating less PB-types of inducers than that of 3-MC type in the Fosu lagoon. This study has indicated that the Fosu lagoon is polluted with 3-MC types and PB-types of inducers and that the 'Roundup'-induced CYP is not only different from the CYP isozymes responsible for the EROD and PROD assays, it actually inactivates them. GST induction indicated in this study would support the effects of the induced CYP in biotransformation of the xenobiotics which enter the fish in polluted waters.