Angiotensin II Stimulates H⁺-ATPase Activity in Intercalated Cells from Isolated Mouse Connecting Tubules and Cortical Collecting Ducts

Abstract

Intercalated cells in the collecting duct system express V-type H⁺-ATPases which participate in acid extrusion, bicarbonate secretion, and chloride absorption depending on the specific subtype. The activity of H⁺-ATPases is regulated by acid-base status and several hormones, including angiotensin II and aldosterone. Angiotensin II stimulates chloride absorption mediated by pendrin in type B intercalated cells and this process is energized by the activity of H⁺-ATPases. Moreover, angiotensin II stimulates bicarbonate secretion by the connecting tubule (CNT) and early cortical collecting duct (CCD). In the present study we examined the effect of angiotensin II (10 nM) on H⁺-ATPase activity and localization in isolated mouse connecting tubules and cortical collecting ducts. Angiotensin II stimulated Na⁺-independent intracellular pH recovery about 2-3 fold, and this was abolished by the specific H⁺-ATPase inhibitor concanamycin. The effect of angiotensin II was mediated through type 1 angiotensin II receptors (AT₁-receptors) because it could be blocked by saralasin. Stimulation of H⁺-ATPase activity required an intact microtubular network - it was completely inhibited by colchicine. Immunocytochemistry of isolated CNT/CCDs incubated in vitro with angiotensin II suggests enhanced membrane associated staining of H⁺-ATPases in pendrin expressing intercalated cells. In summary, angiotensin II stimulates H⁺-ATPases in CNT/CCD intercalated cells, and may contribute to the regulation of chloride absorption and bicarbonate secretion in this nephron segment.

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