Biotransformation and other toxicological and physiological responses in rainbow trout ( Salmo gairdneri Richardson) caged in a lake receiving effluents of pulp and paper industry

Abstract

Hatchery reared immature rainbow trout ( Salmo gairdneri Richardson) were transferred to eight field stations at the southern Lake Saimaa (SE Finland). They were caged in the receiving water body of effluents from a mill producing chlorine bleached kraft pulp and printing paper. The controls were caged upstream to the sewer. The microsomal cytochrome P-450 content, NADPH cytochrome c reductase and monooxygenase enzyme activities as well as conjugation reactions with glucuronic acid and glutathione were studied in the liver, kidney and gills. Conjugated metabolites of chlorophenolics in the bile and some physiological blood parameters were investigated. The caging in polluted water increased the monooxygenase enzyme activities. Compared to control trout, up to 7 times induction of liver 7-ethoxyresorufin O-deethylase (EROD) activity was observed at the nearest caging station, 3 km from the effluent outlet. Activity of EROD was the best indicator for the induction caused by pulp and paper mill effluent, however, pentoxyresorufin O-dealkylase was also responsive. Analysis of conjugated chlorinated phenolics in the bile showed highest concentrations at the caging station nearest to the mill and displayed good distance related decreases. The levels of conjugated toxicants found in control fish indicated a low contamination of the whole southern Lake Saimaa.