THE EFFECTS OF ACUTE COPPER STRESS ON TCA CYCLE AND FREE RADICAL METABOLISM IN THE LIVER OF HOPLOBATRACHUS CHINENSIS

In this study, we applied acute toxicity test to investigate the toxic effects of copper ion(Cu2+) on tricarbo-xylic acid cycle(TCA) and free radical metabolism in the mitochondria of the liver of Hoplobatrachus chinensis. We treated the animals with Cu2+ at different concentrations and for different exposure time, and tested the activities of TCA-related enzymes and free radicals. We found that although Cu2+ at high concentrations could reduce the activity of ICDHm, prolonged exposure time had no significant effect on ICDHm(P 0.05). We did not observe cross effects between the concentration of Cu2+ and the exposure time on the activity of ICDHm(P 0.05). However there were significant cross effects between the exposure time and the concentration of Cu2+ on the activity of -KGDH(P 0.05). The activity of -KGDH decreased when exposed to Cu2+, and the lowest activities were detected when the exposure times were 24h and 96h and concentrations were 4.0 and 6.0 mg/L. In terms of free radical metabolism, the exposure time and copper concentration had strong cross effects on the activities of anti-O2 and H2O2 (P 0.05), but not on the activity of inhibit-OH, the content of NO, and the activity of NOS. The activities of anti-O2 decreased along with the increase in the concentration of Cu2+. The content of H2O2 increased after the treatments and perked at 24h and 6.0 mg/L. There was a negative correlation between the activity of inhibit-OH and the exposure time and the concen-tration of Cu2+. Along with the increase in the concentration of Cu2+, the content of NO and the activity of NOS first increased and then decreased to the values of the control group, and the maximum values appeared in the 6.0 mg/L group. Our study demonstrated that the acute exposure of Cu2+ could have significant toxic effects on TCA cycle and free radical metabolism in the mitochondria of the liver of H. chinensis.