Figure 4.

Direct and indirect effects of aldosterone in mediating shift of K⁺ into the intracellular space. Increases in plasma K⁺ directly stimulates the release of aldosterone from the zona glomerulosa cells of the adrenal gland. Aldosterone binds to the mineralocorticoid receptor inside the cell and increases cell Na⁺ concentration by increasing the activity of the Na⁺-H⁺ exchanger and the Na⁺-K⁺-2Cl^– cotransporter. Increases in cell Na⁺ concentration along with a direct effect of aldosterone leads to increase activity of the Na⁺-K⁺-ATPase pump causing K⁺ uptake. Aldosterone binds to receptors in the central nervous system, causing increased sympathetic outflow, which further stimulates pump activity through β₂-adrenergic receptors. Not shown is that increased sympathetic activity can stimulate insulin release from the pancreas, providing an additional mechanism to augment cell K⁺ uptake. A generic cell is provided to indicate identified transporters involved in K⁺ uptake such as skeletal muscle myocytes, hepatocytes, adipocytes, and cardiac myocytes. Circled+sign, stimulatory effect.