Metabolic requirements for active sodium transport stimulated by aldosterone.

The stimulation in vitro of sodium transport in the toad bladder by aldosterone and other mineralocorticoids is well established (l-3). Sodium transport is stimulated by physiological concentrations of aldosterone, and the effect of aldosterone is inhibited by spirolactones, progesterone, and ouabain (4). Evidence has been obtained which suggests the involvement of protein synthesis in the mechanism of action of aldosterone (5, 6). Since the transport of sodium by the toad bladder is an active process requiring expenditure of energy derived from the metabolism of the tissue, it became of interest to determine the metabolic requirements for the hormonal effect. It has been shown that in the fresh tissue the hormone elicits its characteristic stimulation, but after a period of incubation of the tissue so as to deplete it of its endogenous substrat’e, the hormonal effect is demonstrable only upon addition of pyruvate, and substrates which yield pyruvate during the course of their metabolism (7), as well as fl-hydroxybutyrate and acetoacetate (8, 9). In the absence of aldosterone these substrates are without effect (7, 9). The present paper examines further the metabolic basis for the effect of aldosterone on sodium transport.