pharmacology

At the late distal tubule and collecting duct, aldosterone has two main actions: 1) aldosterone acts on mineralocorticoid receptors (MR) on principal cells in the distal tubule of the kidney nephron, increasing the permeability of their apical (luminal) membrane to potassium and sodium and activates their basolateral Na+/K+ pumps, stimulating ATP hydrolysis leading to phosphorylation of the pump and a conformational change in the pump exposes the Na+ ions to the outside. The phosphorylated form of the pump has a low affinity for Na+ ions, hence reabsorbing sodium (Na+) ions and water into the blood, and secreting potassium (K+) ions into the urine; 2) aldosterone stimulates H+ secretion by intercalated cells in the collecting duct, regulating plasma bicarbonate (HCO3−) levels and its acid/base balance; and 3) aldosterone may act on the central nervous system via the posterior pituitary gland to release vasopressin (ADH) which serves to conserve water by direct actions on renal tubular resorption.