Impaired acid secretion in cortical collecting duct intercalated cells from H-K-ATPase-deficient mice: role of HKa isoforms

摘要

at least two H-K-ATPase a-subunits (HKa) are expressed in the collecting duct (CD): the HKai (gastric) and the HKa2 (colonic). These enzymes function in renal acid-base balance and potassium homeostasis (25). The a-subunit is the catalytic subunit and is essential for proton (H) and potassium (K) pumping. It assembles with a p-subunit to form the functional H-K-ATPase enzyme (20). Although previous studies reported the contribution of each H pump based on pharmacological inhibition and other studies reported the enzymatic activity in knockout mice, the contribution of each pump to net cellular H extrusion or the effects of the combined knockout have not been quantified. One or both pumps play a role in K reabsorp-tion during K depletion.