Branchial versus Intestinal Silver Toxicity and Uptake in the Marine Teleost Parophrys Vetulus

Exposure to elevated waterborne silver as AgNO 3 (4.07 lM=448 lg l ±1) in seawater resulted in osmoregulatory disturbance in the lemon sole (Paroph-rys vetulus). The main e€ects were increased plasma Na + and Cl ± concentrations which translated into increased plasma osmolality. Plasma Mg 2+ levels were also slightly increased after 96 h exposure. Using radio-isotopic ¯ux measurements, a 50% reduction in bran-chial unidirectional Na + extrusion was observed after 48 h silver exposure. By applying an intestinal perfusion approach, we were able to separate and thus quantify the intestinal contribution to the observed silver-induced physiological disturbance and internal silver accumulation. This analysis revealed that the intestinal contribution to silver-induced ionoregulatory toxicity was as high as 50±60%. In marked contrast, internal silver accumulation (in liver and kidney) was found to be derived exclusively from uptake across the gills. Drinking of silver-contaminated seawater resulted in substantial silver accumulation in the intestinal tissue (but apparently not silver uptake across the intestine), which probably explains the intestinal contribution to silver-induced physiological disturbance.