Brown Chang Rockfish (sebastiscus,, Marmoratus) Liver Microsomal Cytochrome P-450 Monooxygenase - Kinetics Of The Reaction Conditions, Induction And Monitoring

Using 7-ethoxyresorufin as substrate, the kinetic contants Km and Vmax, optimal conditions of hepatic EROD reaction system in scorpionfish (Sebastiscus marmoratus) were studied in controlled and induced groups exposed to 0# diesel oil water-accommodated fraction (WAF). And based on kinetic study, the optimal conditions of hepatic EROD assay were established. After dose-response experiment and time-course experiment of hepatic EROD, the minimal dose and time for significant induction of the enzyme were determined in scorpionfish. Moreover caged scorpionfish were exposed to field pollution at 6 sites in Xiamen West Harbor for one month and the hepatic EROD activity was taken as a biomarker to evaluate the quality of coastal water, combined with chemical analyses of Cd and oil contaminants in the sediment and in the water, respectively. In addition, the dose-response experiment of hepatic EROD in porgy (Spams latus) induced by 0# disel oil WAF was studied to dsicuss the possibility to use it as a biomarker for monitoring environmental pollution. The results indicated:1. For hepatic Cyt.P-450 EROD of scorpionfish, the optimal conditions for the enzyme reaction system were pH7.6 and 15℃. Km and Vmax of the hepatic EROD reaction system were 0.144μM and 0.466 nmol/min/mg in controlled group, and 0.357μM and 2.360nmol/min/mg respectively in the induced group by l00μg/L of 0# diesel oil WAF.2. Exposed to WAF of 0# diesel oil at 10ug/L~100ug/L, the EROD activity from the induced scorpionfish livers increased in different contents, compared to the controlled group. One-way ANOVA showed that EROD activity was significantly increased, and EROD activity had a good linear correlation with concentrations of the WAF(R2=0.98).3. Exposed to the WAF of 0# diesel oil at 40μ.g/L for 4 days, hepatic EROD activity from the induced scorpionfish reached a maximal level by contrast with the controlled group. After 6 days of the exposure, EROD activitydecreased in general. The activity decreasement might be caused by inhibition of the oil WAR4. The results of environmental monitoring in Xiamen West Harbor showed that hepatic EROD activity of scorpionfish was correlated with oil concentration at different sites, specially with a higher oil contamination at the First Port. Our result indicates that it is feasible to use hepatic EROD activity of scorpionfish as a biomarker for monitoring environmental pollution of oil and PAHs.5. Exposed to the WAF of 0# diesel oil at 10g/L~100g/L, the EROD activity from porgy livers increased in contrast to the controlled group. It reached maximal activity (up to 13.30-fold) at the concentration of 75g/L, followed by an apparent reduction when the concentration of the WAF increased to l00g/L. The phenomena could be explained by competitive inhibition of the EROD enzyme-substrate reaction. Although one-way ANOVA showed that EROD activities in the groups were not statistically significant, the enzyme activity at 75g/L shew significant difference from that at the control group by t-test. In comparison, each induced group of hepatic EROD activity from porgy increased in a higher degree than that from scorpionfish at the same dose of the WAF, and was suppressed at l00g/L in porgy but not in scorpionfish. Thus it appears that porgy was more sensitive to the WAF than scorpionfish at the low dose, but less tolerant at the high dose.