Characterization of hepatic and extrahepatic glutathione S-transferases in rainbow trout (Oncorhynchus mykiss) and their induction by 3,3 ',4,4 '-tetrachlorobiphenyl

Liver, kidney, gill and olfactory epithelium cytosolic fractions of rainbow trout (Oncorhynchus mykiss) were examined for glutathione S-transferase (GST) contents. Proteins retained on a glutathione (GSH)-affinity matrix were separated as monomers by reversed-phase HPLC and characterized by immunoblotting, mass spectrometry and partial amino acid sequence. For each organ concerned, a specific pattern of these proteins was determined and appeared similar for liver and kidney on one hand, and for gill and olfactory epithelium on the other hand. It was confirmed that the prominent hepatic GST is a class pi enzyme, also constitutively expressed as a major isoform in the four organs studied. Moreover, a class pi variant and two new class mu GST subunits were characterized in minor fractions. An unknown protein, which was found major in gills and olfactory epithelium, exhibited some characteristics of class theta GSTs. Occurrence of possible GSH-adduct formation observed on two distinct monomers in specific experimental conditions is discussed. These results and methods were used to investigate the effect of 3,3',4,4'-tetrachlorobiphenyl (TCB), a polychlorinated biphenyl (PCB), on GST expression in trout liver. From HPLC-profiling, significant co-induction of the major class pi and the two minor class mu GST subunits was observed in trout after waterborne exposure to TCB which was followed by a slight increase in 1-chloro-2,4-dinitrobenzene (CDNB) activity. The present work allows qualitative evaluation of the specific detoxification potential of rainbow trout. The use of HPLC-profiling of GSTs as a possible tool for the biomonitoring of polluted aquatic environment is suggested.