TY - JOUR
T1 - Calcium/cadmium interactions at uptake surfaces in rainbow trout
T2 - Waterborne versus dietary routes of exposure
AU - Franklin, Natasha M.
AU - Glover, Chris N.
AU - Nicol, James A.
AU - Wood, Chris M.
PY - 2005/11
Y1 - 2005/11
N2 - Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to control, 3 μg/L waterborne Cd, or 500 mg/kg dietary Cd in combination with either a control (20 mg/g Ca2+ as CaCO3) or elevated (60 mg/g Ca2+) Ca2+ diet for 28 d. No mortality or growth effects were observed in response to either route of Cd exposure, although fish fed Ca2+-supplemented diets exhibited minor reductions in growth within the first few days of feeding. Waterborne and dietary Cd resulted in significant Cd accumulation in most tissues, with dietary uptake being far in excess of waterborne under the exposure conditions used. The order of Cd accumulation strongly reflected the exposure pathway, being gill and kidney > liver > gut > carcass (waterborne Cd); gut > kidney > liver > gill > carcass > bone (dietary Cd). On a whole-body basis, the net retention of Cd from the diet was <1%, indicating that the gut wall forms an important protective barrier reducing Cd accumulation into internal tissues. Dietary Ca2+ supplementation reduced short-term whole-body uptake rates of waterborne Ca2+ and Cd by >50% and resulted in much lower chronic accumulation of Cd (via the water and diet) in target tissues. Results suggest that Ca2+ and Cd share common pathway(s)/transport mechanism(s) in the gill and gut and that increased gastrointestinal Ca2+ uptake likely caused downregulation of branchial and gastrointestinal Ca2+ and therefore Cd uptake pathways. Because nutrient metals other than Ca 2+ may also influence Cd (and other metal) uptake, new regulatory approaches to metal toxicity (e.g., biotic ligand model) require understanding of the influence of dietary status on metal accumulation.
AB - Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to control, 3 μg/L waterborne Cd, or 500 mg/kg dietary Cd in combination with either a control (20 mg/g Ca2+ as CaCO3) or elevated (60 mg/g Ca2+) Ca2+ diet for 28 d. No mortality or growth effects were observed in response to either route of Cd exposure, although fish fed Ca2+-supplemented diets exhibited minor reductions in growth within the first few days of feeding. Waterborne and dietary Cd resulted in significant Cd accumulation in most tissues, with dietary uptake being far in excess of waterborne under the exposure conditions used. The order of Cd accumulation strongly reflected the exposure pathway, being gill and kidney > liver > gut > carcass (waterborne Cd); gut > kidney > liver > gill > carcass > bone (dietary Cd). On a whole-body basis, the net retention of Cd from the diet was <1%, indicating that the gut wall forms an important protective barrier reducing Cd accumulation into internal tissues. Dietary Ca2+ supplementation reduced short-term whole-body uptake rates of waterborne Ca2+ and Cd by >50% and resulted in much lower chronic accumulation of Cd (via the water and diet) in target tissues. Results suggest that Ca2+ and Cd share common pathway(s)/transport mechanism(s) in the gill and gut and that increased gastrointestinal Ca2+ uptake likely caused downregulation of branchial and gastrointestinal Ca2+ and therefore Cd uptake pathways. Because nutrient metals other than Ca 2+ may also influence Cd (and other metal) uptake, new regulatory approaches to metal toxicity (e.g., biotic ligand model) require understanding of the influence of dietary status on metal accumulation.
KW - Cadmium
KW - Calcium
KW - Dietary exposure
KW - Rainbow trout
KW - Waterborne exposure
UR - http://www.scopus.com/inward/record.url?scp=27144532803&partnerID=8YFLogxK
U2 - 10.1897/05-007R.1
DO - 10.1897/05-007R.1
M3 - Journal Article
C2 - 16398134
AN - SCOPUS:27144532803
SN - 0730-7268
VL - 24
SP - 2954
EP - 2964
JO - Environmental Toxicology and Chemistry
JF - Environmental Toxicology and Chemistry
IS - 11
ER -