Kinetics of radiolabelled silver uptake and depuration in the gills of rainbow trout (Oncorhynchus mykiss) and European eel (Anguilla anguilla):The influence of silver speciation

• Published in: Aquatic Toxicology
• Main Authors: Wood, C.M., Grosell, M., Hogstrand, C., Hansen, Heinz Johs. Max
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2002
• Subjects: 10-S miljø; Anguilla anguilla; European eel
• Online Access: https://orbit.dtu.dk/en/publications/c496f255-e533-4137-9e54-8488f7ce929d; https://doi.org/10.1016/S0166-445X(01)00182-5

We examined the influence of speciation on the kinetics of silver uptake and deputation in the gills of two freshwater fish, the rainbow trout (Oncorhynchus mykiss) which has high branchial Na+ and Cl- uptake rates and is relatively sensitive to silver, and the European eel (Anguilla anguilla, yellow stage) which has low ion uptake rates and is relatively resistant to silver. Fish previously acclimated to the appropriate chloride level were exposed to (110m) AgNO3 (1.3 mug 1(-1), sublethal) for 24 h in synthetic softwater with either low (10 muM) or high (1200 muM) chloride concentration, and then followed over a subsequent 67-day post-exposure period in silver-free water of the same chloride content. The exposures were therefore mainly to the free ion, Ag+ in the low chloride water versus mainly to the neutral aqueous complex, AgClaq in the high chloride water. In trout, but not in eel. water chloride is known to protect against physiological disturbances and toxicity caused by Ag+. In both fish species, at both chloride levels, silver uptake exhibited complex kinetics. Gill silver loading occurred slowly until 6 h, then rose greatly to a peak at 12 h, followed by significant net depuration thereafter during continued exposure. By 24 h, net gill loading was three-to fivefold greater from AgClaq than from Ag+ exposure in both species, and threefold greater in trout than in eel under both conditions, with trout holding a lower fraction of the whole body burden in their gills, During the post-exposure period, depuration of silver from the gills occurred rapidly in trout, but very slowly in eel, such that gill silver burdens were greater in eel throughout the 67-day period on both an absolute and relative basis (e.g. 35% of whole body burden in eel versus < 3% in trout at day 8). The kinetics of depuration were described by two phase exponential models, with break points between the fast and slow phases at I and 15 days for trout and eel, respectively. We conclude that speciation affects not only uptake rates ...