Endocrine influences on the net extrarenal fluxes of sodium and potassium in the European eel (Anguilla anguilla L.).

Abstract

SUMMARY By use of the 'eel tube', it was shown in the freshwater eel that there was a regular net influx (gain) of sodium and a net outflux (loss) of potassium in quiescent animals with steady and normal respiration. Adaptation of eels to distilled water for periods of up to 6 weeks resulted in an increased net extrarenal (gills) uptake of sodium and an increased net loss of potassium when the head of the animal was placed in tap water made up to 600 μmoles Na+. Stress, injection of cortisol, metyrapone, metyrapone plus betamethasone and aldactone reduced or abolished net sodium gain and had variable effects on net potassium loss. The injection of aldosterone or a potassium chloride solution, but not that of a sodium chloride solution, produced an increased net gain of sodium. Removal of the corpuscles of Stannius was without demonstrable effect on net sodium and potassium fluxes; they remained within the normal range. Hypophysectomy reduced net sodium gain. Adrenalectomy markedly diminished or abolished net sodium gain with increased potassium loss. Net sodium gain was restored to normal values by injection of aldosterone. These results are discussed with regard to the homeostatic mechanisms in the euryhaline teleosts.