INFLUENCE OF SEASONAL-CHANGES IN WATER TEMPERATURE ON CADMIUM INDUCIBILITY OF HEPATIC AND RENAL METALLOTHIONEIN IN RAINBOW-TROUT

Changes in metallothionein (MT) levels in liver and kidney of juvenile rainbow trout (Oncorhynchus mykiss) were followed for 8 months, as th e water temperature was allowed to follow the natural temperature decr ease in Tvaren, a bay in the Baltic Sea. The temperature dropped from 15 degrees C to 2 degrees C during the experimental period. The liver and kidney were analysed for MT, zinc, copper and cadmium. Both the he patic and renal MT levels were found to increase in the control group during the first 4 months of the experiment, as the water temperature dropped to 4 degrees C. Once the temperature had stabilized at 2 degre es C there was a noticeable decrease in both hepatic and renal MT leve ls. One group of fish was exposed to water-borne cadmium (100 mu g Cd/ litre) for the duration of the experiment. Cadmium accumulated in both liver and kidney, and reached the highest levels in the kidney. Expos ure of the fish to cadmium resulted in marked elevations of kidney MT levels. In the liver the MT levels did not increase above the control levels as the temperature dropped io 2 degrees C after 6 months. Howev er, once the temperature stabilized at 2 degrees C (after 8 months) th e hepatic MT levels were significantly higher in cadmium-exposed fish than in the control fish. Copyright (C) 1996 Elsevier Science Ltd