Extrarenal Effects of Aldosterone on Potassium Homeostasis

The role of aldosterone in regulating K+ excretion in the distal nephron is well established in kidney physiology. In addition to effects on the kidney, aldosterone modulates K+ and Na + transport in salivary fluid, sweat, airway epithelia, and colonic fluid. More controversial and less well defined is the role of aldosterone in determining the internal distribution of K+ across cell membranes in nontransporting epithelia. In vivo studies have been limited by the difficulty in accurately measuring overall K+ balance and factoring in both variability and secondary changes in acid-base balance, systemic hemodynamics, and other K+ -regulatory factors such as hormones and adrenergic activity. Despite these limitations, the aggregate data support a contributory role of aldosterone along with insulin and catecholamines in the normal physiologic regulation of internal K+ distribution. The authors speculate differences in tissue sensitivity to aldosterone may also contribute to differential tissue response of cardiac and skeletal muscle to conditions of total body K+ depletion.