McCance & Huether's Pathophysiology Test 1 Practice Test

Aldosterone acts on the distal nephron (distal tubule and collecting ducts) to promote sodium reabsorption. It increases the activity of Na+/K+-ATPase on the basolateral membrane and upregulates sodium channels (ENaC) on the apical membrane, pulling sodium back into the bloodstream. This sodium retention pulls water with it osmotically, helping to maintain extracellular fluid volume and blood pressure. Potassium secretion into the urine is a secondary effect, but the primary action is sodium reabsorption. Calcium reabsorption is not a main target of aldosterone, and it does not decrease water reabsorption.