title: The mechanisms and costs of physiological and toxicological acclimation to waterborne silver in juvenile rainbow trout (Oncorhynchus mykiss).
abstract: Juvenile rainbow trout were exposed to 0, 0.1, 1, 3, and 5 micro g/l silver (Ag, as AgNO3) for 23 days. Specific growth rate, cumulative food consumption, food-conversion efficiency, and critical swimming speed (U(crit)) were significantly reduced during 5 micro g/l Ag exposure, demonstrating a physiological cost of silver acclimation. Only the 5 microg/l Ag treatment had significant cumulative mortality (5.2%). Fish were most susceptible to silver on days 5 and 15. Exposure to 5 microg/l Ag significantly lowered plasma Na+ and Cl- on days 5 and 10, but plasma ion concentration recovered thereafter. Unidirectional Na+ uptake and gill Na/K-ATPase activity were significantly inhibited by 3 and 5 microg/l Ag exposure. Na+ uptake was inhibited by 3 micro g/l Ag at day 5 alone, whereas the effects at the highest Ag exposure persisted until day 15. Gill Na/K-ATPase was inhibited on day 5 in both the 3 and 5 microg/l Ag treatments but increased to approx. 1.5 times of control levels by day 23. Only the 3 and 5 microg/l Ag treatments produced toxicological acclimation (at least twofold elevations in 168-h LC50 values in fish subsampled on days 15 and 23). We conclude that physiological acclimation results from compensatory changes in Na+ transport at the gills, and that these changes may eventually lead to toxicological acclimation.
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D002712:Chlorides / Q000097:blood; D004781:Environmental Exposure; D005618:Fresh Water / Q000737:chemistry*; D005880:Gills / Q000201:enzymology; D009026:Mortality; D017686:Oncorhynchus mykiss / Q000502:physiology*; D012834:Silver / Q000008:administration & dosage*; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013550:Swimming / Q000502:physiology; D013997:Time Factors
chemical_list: D002712:Chlorides; D012834:Silver; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase