The site of the aldosterone induced stimulation of sodium transport

Abstract The content and concentration of major ions within the scraped mucosal epithelial cells of the urinary bladder of the toad Bufo marinus were determined using [ 14 C]- and [ 3 H]-inulin to correct for adherent extracellular fluid. In aldosterone treated hemi-bladders the radioactive sodium content and concentration increased significantly as compared with paired control hemi-bladders when both tissues were exposed to [ 24 Na] in the mucosal bathing medium. Changes in total non-inulin space sodium were not detected but the stimulation of transepithelial sodium transport by aldosterone in this set of observations was small, averaging only some 30% above control. The results are compatible with our hypothesis that the major action of aldosterone is to facilitate the entry of sodium from the mucosal medium across the apical permeability barrier of the transporting mucosal cells.