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(IP53) Dietary versus waterborne copper exposure in rainbow trout: uptake and turnover during acclimation to waterborne copper.
Kamunde, C*,1, Wood, C1, 1 McMaster University, Hamilton, ON, Canada
ABSTRACT- Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to an environmentally realistic waterborne Cu level (22 g/L) in moderately hard water for up to 28 days. Unidirectional copper uptake rates from both the diet and water were assessed weekly using 64Cu radiolabeled diets and water. Relative to control fish kept at background Cu concentration (2 g/L), Cu pre-exposed fish displayed decreased uptake of waterborne Cu via the gills but not decreased uptake of dietary Cu via the gut during 48-h exposures to 64Cu radiolabeled water and diet, respectively. At normal dietary and waterborne Cu levels, the uptake rates of dietary Cu into the whole body (without the gut) were between 0.40 and 0.90 ng/g/h, more than 10-fold higher than those of waterborne Cu into the whole body (without the gills), which were between 0.02 and 0.07 ng/g/h. Waterborne Cu pre-exposed decreased new Cu accumulation in the gills, liver, and carcass during waterborne 64Cu exposures and in the liver during dietary 64Cu exposures. A 3-h gill Cu-binding assay showed down-regulation of the putative high affinity-low capacity Cu transporters and up-regulation of the low affinity-high capacity Cu transporters at the gills in Cu pre-exposed fish. Exchangeable Cu pools in all the tissues sampled were higher during dietary 64Cu exposures than waterborne 64Cu exposures, and previous Cu exposure reduced waterborne exchangeable Cu pools in gill, liver, and carcass. Overall, these results underline a quantitatively greater role for the dietary route of Cu uptake relative to the waterborne route, and important modifications of Cu uptake and transport mechanisms following waterborne Cu pre-exposure. (Supported by NSERC Strategic, MITE-RN, ICA, ILZRO, NiPERA, Falconbridge, Cominco, and Noranda).
Key words: copper, dietary and waterborne uptake, turnover, acclimation
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