Angiotensin II stimulates vacuolar H+-ATPase activity in renal acid-secretory intercalated cells from the outer medullary collecting duct

Abstract

Final urinary acidification is mediated by the action of vacuolar H +-ATPases expressed in acid-secretory type A intercalated cells (A-IC) in the collecting duct. Angiotensin II (AngII) has profound effects on renal acid-base transport in the proximal tubule, distal tubule, and collecting duct. This study investigated the effects on vacuolar H+-ATPase activity in A-IC in freshly isolated mouse outer medullary collecting ducts. AngII (10 nM) stimulated concanamycin-sensitive vacuolar H+-ATPase activity in A-IC in freshly isolated mouse outer medullary collecting ducts via AT1 receptors, which were also detected immunohistochemically in A-IC. AngII increased intracellular Ca2+ levels transiently. Chelation of intracellular Ca2+ with BAPTA and depletion of endoplasmic reticulum Ca2+ stores prevented the stimulatory effect on H+-ATPase activity. The effect of AngII on H+-ATPase activity was abolished by inhibitors of small G proteins and phospholipase C, by blockers of Ca2+-dependent and -independent isoforms of protein kinase C and extracellular signal-regulated kinase 1/2. Disruption of the microtubular network and cleavage of cellubrevin attenuated the stimulation. Finally, AngII failed to stimulate residual vacuolar H+-ATPase activity in A-IC from mice that were deficient for the B1 subunit of the vacuolar H+-ATPase. Thus, AngII presents a potent stimulus for vacuolar H+-ATPase activity in outer medullary collecting duct IC and requires trafficking of stimulatory proteins or vacuolar H+-ATPases. The B1 subunit is indispensable for the stimulation by AngII, and its importance for stimulation of vacuolar H+-ATPase activity may contribute to the inappropriate urinary acidification that is seen in patients who have distal renal tubular acidosis and mutations in this subunit. Copyright © 2007 by the American Society of Nephrology.