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Titre du Document
The mechanism of acute silver nitrate toxicity in freshwater rainbow trout (Oncorhynchus mykiss) is inhibition of gill Na+ and Cl transport
Auteur(s)
MORGAN I. J. ; HENRY R. P. ; WOOD C. M.
Résumé
Copyright (c) 1997 Elsevier Science B.V. All rights reserved. Rainbow trout (Oncorhynchus mykiss) were exposed to 2 and 10μgl−1 silver (as AgNO3) for up to 75h in moderately hard freshwater. At 10μgl−1 total Ag, branchial Na+ and Cl influxes were inhibited by over 50% immediately and by almost 100% at 8h, and showed no signs of recovery over the duration of the experiment. Na+ and Cl effluxes were much less affected. These changes in unidirectional fluxes resulted in a large net loss of both Na+ and Cl across the gills and a significant decrease in plasma [Na+ and [Cl. The effects of exposure to 2μgl−1 Ag on Na+ and Cl transport were generally similar to those at 10μgl−1, but were of a lesser magnitude. Unidirectional Na+ fluxes recovered immediately after removal of silver, after 48h exposure to 2μgl−1. Michaelis−Menten kinetic analysis demonstrated that the maximal rate of Na+ influx (Jmax) was significantly reduced after 48h exposure to 2μgl−1 Ag, whereas the affinity of the transport sites for Na+ (1/Km) was unaffected, indicating that the inhibition of Na+ influx by silver was of a non-competitive nature. Fish exposed to 10μgl−1 Ag for 48h also had significantly lower activities of the branchial enzymes Na+/K+ ATPase (85% inhibition) and carbonic anhydrase (28% inhibition). The re
Editeur
Elsevier Science
Identifiant
ISSN : 0166-445X CODEN : AQTODG
Source
Aquatic toxicology A. 1997, vol. 38, n° 1-3, pp. 145-163
Langue
Anglais
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