The Role of Aldosterone in Active Sodium Transport

Aldosterone regulation of sodium transport is believed to involve interaction of the steroid with mineralocorticoid-specific, aldosterone-binding proteins. The induction hypothesis holds that this steroid-protein complex stimulates the synthesis of a specific species of RNA. It is postulated that this RNA directs the synthesis of specific proteins which increase Na reabsorption by increasing the activity of a rate-limiting step in the Na transport process. Three theories have been advanced regarding which step in the Na reabsorptive process is stimulated. After critical review of the "sodium permease," the "energy," and the "sodium pump" theories, we conclude that it is not possible to reject any theory at this time.