SUSCEPTIBILITY OF CHANNEL CATFISH (ICTALURUS-PUNCTATUS) AND BROWN BULLHEAD (AMERIURUS-NEBULOSUS) TO OXIDATIVE STRESS - A COMPARATIVE-STUDY

Many pollutants in aquatic systems have been shown to exert toxic effects related to oxidative stress. Biochemical parameters of xenobiotic metabolism and oxidative stress were examined in two benthic fish species, channel catfish and brown bullhead, which differ in their apparent susceptibility to pollutant-mediated neoplasia. These parameters included enzyme activities and production of reactive oxygen species by hepatic subcellular fractions. Hepatic ethoxyresorufin O-deethylase (EROD) activity was markedly higher in catfish than in bullhead. This interspecific difference was also observed following induction of EROD activities by beta-naphthoflavone (betaNF). Conversely, hepatic microsomal cytochrome P-450 reductase (P-450R) activity was higher in bullhead and was unaffected in both species by betaNF treatment. Hepatic catalase, DT diaphorase, glutathione reductase, glutathione S-transferase and total glutathione content were significantly higher in catfish as well. Hepatic glutathione peroxidase activity was significantly higher in bullhead. No significant interspecific difference was observed in hepatic superoxide dismutase activity. Cytosolic rates of menadione-mediated superoxide anion and hydrogen peroxide production were higher in pooled catfish liver samples as compared to bullhead. Conversely, microsomal rates of superoxide and hydrogen peroxide production were higher in bullhead, consistent with relative P-450R activities in the two species. Catfish liver homogenate was more effective than bullhead homogenate at inhibiting iron/ascorbate-mediated production of 8-hydroxydeoxyguanosine (8-OHdG) in vitro.