Cu uptake and turnover in both Cu-acclimated and non-acclimated rainbow trout (Oncorhynchus mykiss)

Cu-64 accumulation and total Cu concentration were measured in plasma, red blood cells, gills, liver, kidney and bile during 65 h of exposure to Cu-64 at 20 mu g of Cu per liter, in non acclimated and Cu acclimated (28 days of preexposure) rainbow trout (Oncorhynchus mykiss) fitted with a dorsal aortic catheter. By measuring both Cu-64 accumulation and total Cu concentrations, we were able to analyse the ongoing uptake and turnover of ambient Cu, independent of any Cu already present in the fish.

Plasma accounted for at least 90% of the Cu-64 labelled Cu present in the blood and Cu-acclimation clearly involves changes in copper accumulation kinetics in the plasma. The acclimated fish showed a 65% reduced Cu-64 accumulation after 65 h and an increased turnover of Cu in the plasma compared to the non-acclimated fish. Total Cu in the plasma increased by 59% after 3 h of exposure in the non-acclimated fish but was recovered during the following 24 h and remained at control levels throughout 65 h; even after 28 days the acclimated fish showed no increase in total plasma [Cu]. Apparently Cu acclimation involves an increased clearing of plasma Cu, primarily to the liver, stimulated during the first 12 h of exposure.

Acclimation did not have an unambiguous effect on branchial Cu uptake and differences in branchial uptake could not explain the reduced accumulation in the plasma. The rapidly exchangeable Cu pools were 54% in the gills and 33% in the liver, suggesting a considerable hepatic Cu elimination. No increase in the total [Cu] in the kidney was observed, but the kidney did show substantial Cu-64 accumulation and thus also a potential renal Cu excretion. (C) 1997 Elsevier Science B.V.