Vasopressin V1a Receptor of Renal Collecting Duct Intercalated Cells Promotes Urinary Proton Secretion

Antagonists of the V1a vasopressin receptor (V1aR) are emerging as a therapeutic strategy for retardation of chronic kidney disorders. Physiologically, V1aR signaling has been linked with acid‐base homeostasis, although the underlying mechanisms remain debatable. In this study, we tested the hypothesis that V1aR activation in type A intercalated cells (A‐ICs) induces urinary H+ secretion. We generated an anti‐V1aR antibody and verified its specificity using V1aR‐knockout tissues. Localization studies in mice, rat and human tissue, were preformed using immunofluorescence and confocal microscopy or 3D‐structured illumination microscopy (3D‐SIM). For functional studies in vivo , V1aR‐specific agonist, AO‐4‐67, was administered in AVP‐deficient Brattleboro rats and C57/BI6J mice (0.2, 2, or 10μg/kg b.w.; 1 to 4h). Urine was collected in metabolic cages or via ureteral catheter and plasma samples were taken. Isolated, microperfused mouse collecting ducts were analyzed for V1aR‐dependent luminal pH changes and cultured inner medullary collecting duct cells for proton‐secreting vH + ‐ATPase regulation. Localization of V1aR in mouse, rat and human kidneys produced basolateral signal in A‐ICs and perinuclear to subapical signal in type B intercalated cells of connecting tubules and collecting ducts throughout these species. In addition, basolateral V1aR signal was detected in macula densa cells of mouse but not rat or human kidneys. Administration of the V1aR agonist, A0‐4‐67, significantly decreased urinary pH in vasopressin‐deficient Brattleboro rats (10 μ g/kg body weight for 4 hours i.p.; pH 7.38 to 6.71 after 1 hour, P<0.01) and C57/BI6J mice (2 μ g/kg body weight for 1 hour i.p.; pH 7.18 to 6.78 after 20 minutes, P<0.05). Basolateral treatment of isolated perfused medullary collecting ducts with the V1aR agonist or vasopressin increased intracellular Ca2+ levels in intercalated cells and decreased luminal pH (pH −5% after 3 minutes, P<0.05) suggesting V1aR‐dependent Ca2+ release and stimulation of proton secreting proteins. Basolateral treatment of inner medullary collecting duct cells with the V1aR agonist induced luminal translocation of vacuolar H+‐ATPase in A‐ICs (apical signal intensity +93%, P<0.001). In summary, our results show that activation of V1aR contributes to urinary acidification via H+ secretion by A‐ICs, which may have clinical implications for pharmacological targeting of V1aR. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .