Effects of feeding on waterborne silver uptake and depuration in rainbow trout (Oncorhynchus mykiss)

Abstract

Rainbow trout (Oncorhynchus mykiss, ~50 g) were exposed to 0.1 µM AgNO3in ion-poor water (Ca ~300 µM, pH ~7, 13°C) with or without being fed 2% of their body weight daily. Gills, plasma, livers, and bile were sampled after 4 h, 24 h, and 1 week. Feeding did not alter Ag uptake by trout, and did not prevent decreases in plasma Na and Cl caused by Ag. To study Ag depuration, trout were exposed to 0.1 µM AgNO3for one week and then were placed in Ag-free, ion-poor water with or without being fed 1% of their body weight daily. Plasma Ag decreased over the 15-day depuration period (elimination rate, ke= 0.085 day–1), but there were no effects of feeding on Ag depuration. There were no physiological differences between fed and unfed fish except for slightly higher plasma glucose concentrations and higher condition factors in fed fish by the end of the Ag depuration period. Thus, once Ag has entered a fish, subsequent elimination (e.g., from the plasma) is not affected by food-related processes such as biliary excretion or increased metabolic rate, or by external factors like food debris in the water.