COBALT UPTAKE ACROSS THE GILLS OF THE COMMON CARP, CYPRINUS-CARPIO, AS A FUNCTION OF CALCIUM-CONCENTRATION IN THE WATER OF ACCLIMATION AND EXPOSURE

The effect of different calcium concentrations in the uptake of cobalt through the gills of the common carp, Cyprinus carpio, was studies 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 mu M calcium. Co2+ uptake experiments were conducted over a 3-hr period at the same range of calcium concentrati ons. There is a clear decrease in the uptake of Co2+ with increasing c alcium concentrations in the exposure water. Above a calcium concentra tion of 1000 mu M, no effect on Co2+ uptake is observed. The effect of the calcium concentration in the acclimation water is significant, bu t of minor importance. The rate of Ca2+ uptake in gills and blood did not depend on the amount of calcium present in the water. Results of t his study suggest that the effect of calcium on Co2+ uptake involves a direct interaction with the systems involved in the translocation of these metal ions across the gill epithelium.