Internal redistribution of radiolabelled silver among tissues of rainbow trout (Oncorhynchus mykiss) and European eel (Anguilla anguilla): the influence of silver speciation

Influence of water Ag(I) speciation on pharmacokinetics of Ag(I) during a post-exposure period was investigated in rainbow trout (Oncorhynchus mykiss) and European eel (Anguilla anguilla). The rainbow trout is sensitive to waterborne ionic Ag+ whereas the eel is tolerant. The fish were acclimated to either of two chloride concentrations, 10 or 1200 muM, in synthetic soft water and then exposed to a sublethal 24-h pulse of 1.3 mug l(-1) of Ag-110m(l) added as (AgNO3)-Ag-110m in these waters.

The protocol provided exposures to mainly the free ion Ag+ (low chloride water) or mainly AgClaq (high chloride water). Contents and concentrations of Ag-110m(l) in tissues and body fluids were then monitored over a 67-day post-exposure period in Ag(I)-free water of the same chloride levels. Changing the speciation of Ag(l) in the water had no effect on the whole body load of Ag-110m(I), but did result in differences in internal distribution.

In trout, changing water Ag(I) speciation significantly altered elimination or accumulation of Ag(I) in several body compartments. Notably, trout exposed to AgClaq eliminated Ag-110m(l) from the kidney more quickly than trout exposed to Ag(l) primarily as Ag+. This elimination was matched by higher concentrations of Ag-110m in liver of trout exposed to Ag(I) primarily as AgClaq, In eel, shifting speciation from Ag+ to AgClaq hastened elimination of Ag-110m(l) from mid and posterior intestine and increased 1 Ag-110m(I) retention in kidney.

While there was no difference between the two fish species in whole body Ag-110m(I) load, most internal body compartments of trout had higher Ag-110m(I) concentrations than those in eel early in the experiment. Because tissue-specific elimination times were longer in eel than in trout, these differences were generally cancelled by the end of the 67-day depuration period.

The only exception was the liver, which in trout continued to accumulate Ag-110m(I) throughout the experiment but in eel remained unchanged. The combined effect of Ag-110m(l) movements in the two species was that trout retained all their accumulated Ag-110m(I) through the 67-day period, whereas the body burden of Ag-110m(I) in eel was reduced to half initial values by day 67. (C) 2002 Elsevier Science B.V.

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