Angiotensin II activates H+‐ATPase in type A intercalated cells in mouse cortical collecting duct

Abstract

ANG II increases Cl− absorption in the mouse CCD by increasing transcellular transport across type B intercalated cells, through an H+-ATPase and Cl−/HCO3− exchanger (pendrin)-dependent mechanism. Thus, we asked if ANG II induces subcellular redistribution of pendrin or the H+-ATPase, using quantitative immunogold cytochemistry of mouse CCDs perfused in vitro. ANG II (10 nM) application to the bath did not change the subcellular distribution of pendrin or the H+-ATPase in B cells, but increased apical plasma membrane H+-ATPase expression 3-fold in A intercalated cells. To determine if ANG II increases H+-ATPase-mediated H+ secretion, Jt-CO2 was measured under identical conditions. Under basal conditions, HCO3− secretion was observed (Jt-CO2 = −4.2 ± 2.2 pmol/mm/min), while HCO3− absorption (Jt-CO2 = 2.5 ± 1.1 pmol/mm/min, P < 0.05) was observed with ANG II applied to the bath, consistent with apical H+-ATPase activation. Finally, application of the H+-ATPase inhibitor, bafilomycin, generated a more lumen-negative transepithelial voltage, VT, in the presence, but not in the absence of ANG II. Conclusions: ANG II increases apical plasma membrane H+-ATPase expression and function. Increased H+ secretion may increase NaCl absorption by: stimulating apical Cl−/HCO3− exchange by reducing luminal HCO3− concentration and increasing CO2 formation and shunting VT generated by ENaC-mediated Na+ absorption.