Mechanisms of dopamine D 1 and angiotensin type 2 receptor interaction in natriuresis

Abstract

Renal dopamine D 1-like receptors (D 1Rs) and angiotensin type 2 receptors (AT 2Rs) are important natriuretic receptors counterbalancing angiotensin type 1 receptor-mediated tubular sodium reabsorption. Here we explore the mechanisms of D 1R and AT 2R interactions in natriuresis. In uninephrectomized, sodium-loaded Sprague-Dawley rats, direct renal interstitial infusion of the highly selective D 1R agonist fenoldopam induced a natriuretic response that was abolished by the AT 2R-specific antagonist PD-123319 or by microtubule polymerization inhibitor nocodazole but not by actin polymerization inhibitor cytochalasin D. By confocal microscopy and immunoelectron microscopy, fenoldopam translocated AT 2Rs from intracellular sites to the apical plasma membranes of renal proximal tubule cells, and this translocation was abolished by nocodazole. Because D 1R activation induces natriuresis via an adenylyl cyclase/cAMP signaling pathway, we explored whether this pathway is responsible for AT 2R recruitment and AT 2R-mediated natriuresis. Renal interstitial coinfusion of the adenylyl cyclase activator forskolin and 3-isobutly-1-methylxanthine induced natriuresis that was abolished either by PD-123319 or nocodazole but was unaffected by specific the D 1R antagonist SCH-23390. Coadministration of forskolin and 3-isobutly-1-methylxanthine also translocated AT 2Rs to the apical plasma membranes of renal proximal tubule cells; this translocation was abolished by nocodazole but was unaffected by SCH-23390. The results demonstrate that D 1R-induced natriuresis requires AT 2R recruitment to the apical plasma membranes of renal proximal tubule cells in a microtubule-dependent manner involving an adenylyl cyclase/cAMP signaling pathway. These studies provide novel insights regarding the mechanisms whereby renal D 1Rs and AT 2Rs act in concert to promote sodium excretion in vivo. © 2011 American Heart Association, Inc.