2-chlorophenol induced hydroxyl radical production in mitochondria in Carassius auratus and oxidative stress – An electron paramagnetic resonance study Original Research Article

In our previous study, electron paramagnetic resonance (EPR) evidence of reactive oxygen species (ROS) production in Carassius auratus following 2-chlorophenol (2-CP) administration was provided. To further investigate the potential pathway of ROS production, liver mitochondria of C. auratus was isolated and incubated with 2-CP for 30 min. An EPR analysis indicated ROS was produced, and intensities of ROS increased with increasing concentrations of 2-CP. The ROS was then assigned •OH by comparing with Fenton reaction. Either catalase or superoxide dismutase, extinguished •OH completely in the mitochondria mixture. These facts suggested that image and H2O2 contributed to the formation of •OH in mitochondria in C. auratus stressed by 2-CP. Combining previous references and our own data, it is reasonable to suggest that 2-CP is first oxidized by H2O2 present in vivo to form phenoxyl radical under the catalytic action of cellular peroxidase (1); phenoxyl radical oxidizes mitochondria NADH to NAD• in the presence of NADH (2); NAD• reacts with oxygen in vivo to produce image (3); image is spontaneously dismutated by SOD to form H2O2 and O2, which creates a renewable supply of H2O2 as the initiators of the chain reactions until NADH is consumed (4); simultaneously with reaction (4), image reacts with H2O2 to form •OH radical via the Haber–Weiss reaction (5). A strong negative correlation (r = −0.9278, p < 0.01) between glutathione (GSH) pool and •OH production was observed after fish were i.p. injected with 2-CP (250 mg kg−1), indicating the depletion of GSH caused by •OH.