| The objective of this research project was to improve understanding chronic Ni exposure effects and accumulation in juvenile rainbow trout ( Oncorhynchus mykiss). Fish were exposed to two concentrations of Ni (13 and 34 muM Ni) in moderately hard water (80 mg CaCO3/L) for 23d and 35d. Accumulation was quantified in tissue (kidney, gill, liver, white muscle, bile) and subcellular fractions of tissues (kidney, gill). Swim performance (Ucrit), plasma ions (Na+, Ca 2+, Mg2+)and muscle metabolites were measured. The gill and kidney accumulated Ni in a time and exposure concentration dependant manner and accumulation was much higher in these tissues relative to the liver, white muscle and bile. Most Ni accumulated within the metabolically detoxified fraction (MDF) of the cell in the gill and kidney indicating protective effects in both tissues; however, complete detoxification was not observed and elevated concentrations of Ni accumulated in the MSF in both tissues relative to unexposed controls. A decrease in Ucrit in Ni exposed fish was observed in both exposures and a temporary disruption of plasma ion concentrations, particularly Na, was observed during the first week of Ni exposure.Accumulation within the MSF of the gill and kidney appears to be associated with a decrease in plasma Na+, mortality and a reduction in swim performance early in the exposure. However, later in the exposure and once plasma ion homeostasis was re-established, there were elevated concentrations of Ni within the MSF, but with no consistent effect in physiological disruption. In the kidney, accumulation within the heat stable proteins fraction (HSP) was time dependent and the kidney had a greater protective effect from allowing Ni to enter the MSF of the cell relative to the gill. In Ni exposed fish, the gill had a much higher Ni accumulation within the MSF on all sampling days. |
