How does hypokalemia affect the excretion of Bicarbonate?
Loss of potassium from the extracellular space is associated with movement of potassium from the intracellular space to the extracellular space, necessitating movement of protons into cells. The result is lower intracellular pH in cells of the PCT causing activation of the NHE3 in the luminal membrane of this nephron segment. Consequently, there is augmented secretion of H + , leading to more reabsorption of NaHCO 3 during hypokalemia, frequently contributing to the maintenance of metabolic alkalosis. Hypokalemia and the associated fall in PCT intracellular pH also stimulate ammoniagenesis, increasing ammonium ion (NH 4 + ) production and excretion:
Each ammonium appearing in the urine represents the addition of an HCO 3 − to the plasma.
