Kidney potassium handling
Two-thirds of the potassium that is filtered by the glomerulus is passively reabsorbed with sodium and water in the proximal tubule.
After further reabsorption in the ascending limb of loop of Henle via the Na + -K + -2Cl − cotransporter, only about 10% of the filtered load reaches the distal nephron. The ability to secrete potassium begins in the early distal convoluted tubule and progressively increases along the distal nephron into the cortical collecting duct. The rate of potassium secretion by the distal nephron depends on the physiological need. The principal cells in the initial collecting duct and the cortical collecting duct are responsible for potassium secretion through the renal outer medullary potassium (ROMK) and large conductance potassium (BK) channels. In states of potassium depletion, reabsorption of potassium occurs in the collecting duct via the apical H + -K + ATPase on α-intercalated cells.