CYTOTOXICITY OF METALS IN ISOLATED FISH CELLS - IMPORTANCE OF THE CELLULAR GLUTATHIONE STATUS

The study investigates the importance of glutathione (GSH) for protect ion of fish cells against heavy metal stress. The cytotoxicities of si x metal salts to the continuous rainbow trout cell line RTG-2 were det ermined by means of the neutral red (NR) uptake inhibition assay. The rank order of metal cytotoxicities (in terms of NR50 values) were Hg > Cd > Zn > Cu > Pb > Ni. The importance of GSH in determining metal to xicity was assessed by inhibition of its synthesis. A 20 h pretreatmen t of RTG-2 cells with 1 mM buthionine sulfoxime caused sustained reduc tion of cellular GSH level to approximate to 30% of the control value. The effect of GSH depletion on metal cytotoxicity was found to be rel ated to the chemical softness parameter of the metal cations: Cytotoxi cities of the 'soft' metals Hg, Cu and Cd were significantly increased in GSH-depleted cells, whereas cytotoxicities of the 'hard' metals Zn , Ni and Pb were not significantly altered. Since chemical softness is a determinant for binding of metal ions to sulfhydryl groups as being present in GSH, the findings of this study suggest that the metal-pro tective effect of GSH in fish cells is, at least partly, due to its ac tion as an intracellular metal chelator; (C) 1998 Elsevier Science Inc . All rights reserved.