Dietary Ca inhibits waterborne Cd uptake in Cd-exposed rainbow trout, Oncorhynchus mykiss

The effects of chronic exposure to waterborne Cd and elevated dietary Ca, a lone and in combination, were examined in juvenile rainbow trout, Oncorhync hus mykiss. Fish were chronically exposed to 0.05 (control) or 2.56 mug/l C d [as Cd(NO3)(2) (.) 4H(2)O] and were fed 2% body mass/day of control (29.6 mg Ca/g) or Ca-supplemented trout food (52.8 mg Ca/g as CaCl2 (.) 2H(2)O). Cd accumulated mainly in gill, liver, and kidney. Waterborne Cd inhibited unidirectional Ca uptake from water into the gill and induced hypocalcemia in the plasma on day 40. Waterborne Cd also induced an elevated Ca concentr ation on day 20 in the gill tissue of trout fed the Ca-supplemented diet an d a decreased Ca concentration on day 35 in the gills of trout fed the cont rol diet. Dietary Ca protected against Cd accumulation in gill, liver, and kidney, but did not protect against the inhibition of Ca uptake into the gi ll or plasma hypocalcemia. When fed Ca-supplemented diet and exposed to wat erborne Cd, fish showed 35% mortality, compared to 0-2% in control fish and in the Cd-exposed fish with normal Ca in the diet. Growth, on the other ha nd, was not affected by any treatment. (C) 2001 Elsevier Science Inc. All r ights reserved.