Intracellular pH as a regulator of Na+ transport

Na reabsorption by tight epithelia, such as frog skin and toad urinary bladder, is highly sensitive to the acid-base status of the cytoplasm. This can be observed in intact epithelia by acidifying the intracellular compartment with acute hypercapnia. Both apical membrane Na channels, which are responsible for the uptake of Na into the cell, and basolateral membrane K channels, which are required for the recycling of K that is actively transported into the cell through the Na/K pump, are shut down by low intracellular pH. This suggests the possibility that cell pH may serve as an important regulator of transport. One possible role is as a second messenger for rapid effects of the adrenal mineralocorticoid aldosterone.