Cobalt uptake across the gills of the common carp, Cyprinus carpio, as a function of calcium concentration in the water of acclimation and exposure

Abstract The effect of different calcium concentrations on the uptake of cobalt through the gills of the common carp, Cyprinus carpio , was studied in chemically defined freshwater. Prior to the cobalt uptake experiments, fish were acclimated for 16 days to different calcium concentrations ranging from 100 to 10,000 μM calcium. Co 2+ uptake experiments were conducted over a 3-hr period at the same range of calcium concentrations. There is a clear decrease in the uptake of Co 2+ with increasing calcium concentrations in the exposure water. Above a calcium concentration of 1000 μM, no effect on Co 2+ uptake is observed. The effect of the calcium concentration in the acclimation water is significant, but of minor importance. The rate of Ca 2+ uptake in gills and blood did not depend on the amount of calcium present in the water. Results of this study suggest that the effect of calcium on Co 2+ uptake involves a direct interaction with the systems involved in the translocation of these metal ions across the gill epithelium.