Movements of potassium, sodium and chloride in incubated gills from the silver eel

Abstract 1. (1) Isolated gills from silver eels adapted to tap water or sea water were incubated aerobically and anaerobically in either tap water or sea water. Net changes in the potassium, sodium and chloride content were determined. 2. (2) Under all incubation conditions isolated gills appeared to be almost completely impermeable to potassium. 3. (3) A constant level of sodium chloride was maintained in isolated gills under aerobic conditions against the normal diffusion gradient to which the eel was adapted. The constant sodium content appeared to result from a steady state in which passive diffusion was balanced by an active movement of sodium in the opposite direction.