Dissociation of the Renin–Aldosterone System and Refractoriness to the Sodium-Retaining Action of Mineralocorticoid During Starvation in Man

The patterns of sodium excretion during starvation and refeeding and their relation to the renin-aldosterone system were examined in a group of healthy volunteers. Subjects in sodium balance experience a brisk natriuresis during the first week of fasting (the natriuretic phase of early starvation) which is followed by a sodium conservation phase if fasting is prolonged. Refeeding with carbohydrate induces an antinatriuretic period. During the natriuretic phase of starvation the aldosterone secretory rate (ASR) rises while plasma renin activity (PRA) falls. In contrast during the anti-natriuretic phase of refeeding ASR falls while PRA increases. In addition early starvation is characterized by a resistance to the sodium-retaining actions of mineralocorticoid. As fasting is continued the sodium-retaining effects of mineralocorticoid are restored. These studies suggest that the metabolic set influences the renin-aldosterone system and the responsiveness of the renal tubule to the sodium-retaining action of both endogenous and exogenous mineralocorticoid.