Metal accumulation and metallothionein in brown trout, Salmo trutta, from two Norwegian rivers differently contaminated with Cd, Cu and Zn

In this work we have studied the accumulation of heavy metals in two brown trout (Salmo trutta) populations in their natural environment and the parti cipation of metal binding to metallothionein (MT) in this process. Cd, Cu a nd Zn concentrations, total MT (including Cu MT) and Cd/Zn MT were measured in the gills, liver and kidney of trout inhabiting two rivers, one Cu-cont aminated and the other Cd/Zn-contaminated, located at Roros, Central Norway . In both populations, high levels of Cu were found in the liver, whereas C d was accumulated in liver and particularly in the kidney. The proportions of Cd/Zn MT and Cu MT in liver and kidney, but not in gills, reflected the accumulated and the environmental concentrations of these metals. The total . Cu MT concentrations in the investigated tissues, however, were highest i n trout from the river with the lowest ambient Cu concentration. It is sugg ested that MTs are of less importance in Cu-acclimated trout. The data also suggest that acclimation to a Cu-rich environment involves reduced Cu accu mulation or increased Cu elimination. In trout from the Cd-rich environment , this metal was mainly bound to MT, whereas in trout from the Cu-rich envi ronment Cd was also associated with non-MT proteins. These findings emphasi ze the importance to determine both Cd/Zn MT and Cu MT levels, when the par ticipation of this protein in metal handling in trout tissues is investigat ed. (C) 2001 Elsevier Science Inc. All rights reserved.