Cu uptake, metabolism and elimination in fed and starved European eels (Anguilla anguilla) during adaptation to water-borne Cu exposure.

64Cu accumulation and total Cu concentrations were measured in gill filaments, plasma, liver and bile of fed and starved European eels (Anguilla anguilla) during 28 days of exposure to 12 and 94 micrograms Cu l-1. Branchial Cu uptake was found to be 0.03 and 0.13 microgram Cu g gill filament-1 h-1 at 12 and 94 micrograms Cu l-1, respectively, throughout 28 days of Cu exposure. At least during exposure to 94 micrograms Cu l-1, the basolateral membrane seemed to be the rate limiting step for branchial Cu uptake. The plasma accounted for at least 70% of the 64Cu labelled Cu present in the blood at both Cu concentrations. The plasma Cu concentration was gradually increased from 0.64 to 1.92 and 2.68 micrograms ml-1 during the first 6 days of Cu exposure; it was partly normalized to 1.07 and 1.45 micrograms ml-1 after 28 days of exposure to 12 and 94 micrograms Cu l-1, respectively, despite a constant branchial Cu uptake, indicating an increased turnover of plasma Cu. The hepatic accumulation of 64Cu was similar in fed and starved eels (0.55 microgram Cu g liver-1 h-1) at both Cu concentrations during the 28 days of exposure. The hepatic total Cu concentrations were lower in the fed fish compared to the starved fish and increased only marginally from 3 to 28 days of exposure indicating a high turnover of hepatic Cu during acclimation. Hepatic Cu elimination, measured as 64Cu in the bile, was highest in the fed fish at the highest Cu concentration and was stimulated during acclimation at least in the starved fish.