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 effe cts related to oxidative stress. Biochemical parameters of xenobiotic metabolism and oxidative stress were examined in two benthic fish spec ies, channel catfish and brown bullhead, which differ in their apparen t susceptibility to pollutant-mediated neoplasia. These parameters inc luded enzyme activities and production of reactive oxygen species by h epatic subcellular fractions. Hepatic ethoxyresorufin O-deethylase (ER OD) activity was markedly higher in catfish than in bullhead. This int erspecific difference was also observed following induction of EROD ac tivities by beta-naphthoflavone (betaNF). Conversely, hepatic microsom al cytochrome P-450 reductase (P-450R) activity was higher in bullhead and was unaffected in both species by betaNF treatment. Hepatic catal ase, DT diaphorase, glutathione reductase, glutathione S-transferase a nd total glutathione content were significantly higher in catfish as w ell. Hepatic glutathione peroxidase activity was significantly higher in bullhead. No significant interspecific difference was observed in h epatic superoxide dismutase activity. Cytosolic rates of menadione-med iated superoxide anion and hydrogen peroxide production were higher in pooled catfish liver samples as compared to bullhead. Conversely, mic rosomal rates of superoxide and hydrogen peroxide production were high er in bullhead, consistent with relative P-450R activities in the two species. Catfish liver homogenate was more effective than bullhead hom ogenate at inhibiting iron/ascorbate-mediated production of 8-hydroxyd eoxyguanosine (8-OHdG) in vitro.