TOXICITY, SILVER ACCUMULATION AND METALLOTHIONEIN INDUCTION IN FRESH-WATER RAINBOW-TROUT DURING EXPOSURE TO DIFFERENT SILVER SALTS

Static-renewal 168-h toxicity tests of silver nitrate (AgNO3), silver chloride (AgCln), and silver thiosulfate (Ag(S2O3)(n)) with juvenile r ainbow trout (Oncorhyncus mykiss) were performed by standard methods. Because of low solubility of AgCl(s), bioassays for AgCln were perform ed in two separate ways. In one test series, AgCl(s) was added to fres hwater and in another, AgCln(aq) was generated by adding AgNO3 to fres hwater supplemented with 50 mM NaCl. Concentrations of Ag and metallot hionein (MT) were analyzed in gills and livers of fish that survived t he exposures. Although Ag added as AgNO, was found to be highly toxic to rainbow trout (168-h LC(50) = 9.1 mu g Ag L(-1)), the toxicities of the other Ag salts were low. The 168-h LC(50) for Ag(S2O3)(n) was 137 ,000 mu g Ag L(-1) and no mortality was observed in AgCln (100,000 mu g Ag L(-1)). Exposure to AgNO3, Ag(S2O3)(n), or AgCln caused accumulat ion of Ag and induction of MT. Highest Ag levels were found in livers of trout exposed to 164,000 mu g Ag L(-1) as Ag(S2O3)(n). In these fis h, the hepatic Ag concentration was increased 335 times from the contr ol value. The MT levels in gills and liver increased with the water Ag concentration and the highest level of MT was found in liver of fish exposed to Ag(S2O3)(n).