Acute waterborne cadmium uptake in rainbow trout is reduced by dietary calcium carbonate

Abstract

The effects of elevated dietary calcium (as CaCO 3) and acute waterborne Cd exposure (50 μg/l) on whole body uptake, tissue uptake, and internal distribution of newly accumulated Cd, Ca 2+, and Na + in juvenile rainbow trout were examined. Fish were fed with three diets (mg Ca 2+/g food): 20 (control), 30 and 60 for 7 days before fluxes were measured with radiotracers. The highest dietary Ca 2+ elevation reduced waterborne whole body Ca 2+ uptake, but did not protect against inhibition of waterborne Ca 2+ uptake by waterborne Cd. Both Ca 2+-supplemented diets reduced newly accumulated Ca 2+ in the gills in relation to the control treatment, but did not prevent the Cd-inhibiting effect against accumulation of new Ca 2+ in most compartments. Fish fed with Ca 2+-supplemented diets showed markedly lower rates of whole body uptake and internalization (in some tissues) of waterborne Cd, illustrating that, while dietary Ca 2+ supplementation did not protect against the impact of waterborne Cd on waterborne Ca 2+ uptake, it did protect against the uptake of Cd. Waterborne Cd had no effect on Na + fluxes, total Cl −, and in most body compartments, newly accumulated Na + and total Na + were also not affected. Dietary supplementation with CaCO 3 had the same protective effect as demonstrated by dietary supplementation with CaCl 2 in an earlier study. Thus, the reduction of waterborne Cd uptake and internalization by dietary Ca 2+ was specifically due to Ca 2+ and not to the anion.