Hepatic metallothionein in a teleost (Prochilodus scrofa) exposed to copper at pH 4.5 and pH 8.0.

Copper accumulation and induction of metallothionein (MT) were investigated in the liver of juvenile Prochilodus scrofa exposed to copper (96 h-LC50) at pH 4.5 (LC50=98+/-0.8 microg Cu l(-1)) and pH 8.0 (LC50=16+/-0.5 microg Cu l(-1)) at 20 degrees C. No significant difference was found in copper accumulated in the liver at either pH. The ratio between copper accumulation in the liver after 96 h exposure and the copper in the water at pH 4.5 and 8.0 was 5.1 and 34.4, respectively. MT in the liver of fish exposed to copper was isolated by DEAE-Sepharose chromatography and identified by SDS-PAGE. No MT was identified in the controls. MT concentration was 126.8+/-21.5 and 167.4+/-25.6 microg g(-1) wet mass in fish exposed to copper at pH 4.5 and pH 8.0 (P>0.05), respectively. The results indicate that the pH of the water is a determining factor in copper toxicity, and the increased concentration of MT in the liver of P. scrofa exposed to copper suggests the possibility of using MT as a biomarker to evaluate the biological response of this species to copper contamination in aquatic environments.