Renal β-intercalated cells maintain body fluid and electrolyte balance
Victor Gueutin, … , Dominique Eladari, Régine Chambrey
Victor Gueutin, … , Dominique Eladari, Régine Chambrey
Published September 24, 2013
Citation Information: J Clin Invest. 2013;123(10):4219-4231. https://doi.org/10.1172/JCI63492.
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Renal β-intercalated cells maintain body fluid and electrolyte balance

Abstract

Inactivation of the B1 proton pump subunit (ATP6V1B1) in intercalated cells (ICs) leads to type I distal renal tubular acidosis (dRTA), a disease associated with salt- and potassium-losing nephropathy. Here we show that mice deficient in ATP6V1B1 (Atp6v1b1–/– mice) displayed renal loss of NaCl, K+, and water, causing hypovolemia, hypokalemia, and polyuria. We demonstrated that NaCl loss originated from the cortical collecting duct, where activity of both the epithelial sodium channel (ENaC) and the pendrin/Na+-driven chloride/bicarbonate exchanger (pendrin/NDCBE) transport system was impaired. ENaC was appropriately increased in the medullary collecting duct, suggesting a localized inhibition in the cortex. We detected high urinary prostaglandin E2 (PGE2) and ATP levels in Atp6v1b1–/– mice. Inhibition of PGE2 synthesis in vivo restored ENaC protein levels specifically in the cortex. It also normalized protein levels of the large conductance calcium-activated potassium channel and the water channel aquaporin 2, and improved polyuria and hypokalemia in mutant mice. Furthermore, pharmacological inactivation of the proton pump in β-ICs induced release of PGE2 through activation of calcium-coupled purinergic receptors. In the present study, we identified ATP-triggered PGE2 paracrine signaling originating from β-ICs as a mechanism in the development of the hydroelectrolytic imbalance associated with dRTA. Our data indicate that in addition to principal cells, ICs are also critical in maintaining sodium balance and, hence, normal vascular volume and blood pressure.

Authors

Victor Gueutin, Marion Vallet, Maximilien Jayat, Janos Peti-Peterdi, Nicolas Cornière, Françoise Leviel, Fabien Sohet, Carsten A. Wagner, Dominique Eladari, Régine Chambrey

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Figure 6

Paracrine signaling in the isolated microperfused CCD.

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Paracrine signaling in the isolated microperfused CCD. (A and B) Measure...
(A and B) Measurement of bafilomycin A1–induced luminal PGE2 release in the isolated microperfused CCD using a biosensor technique. (A) HEK cells overexpressing the EP1 receptor were loaded with Fluo-4 and Fura Red, held by a holding pipette (HP1), and positioned in the lumen of the split-open microperfused CNT/CCD, in contact with the tubular fluid. PP, CCD perfusion pipette; HP2, holding pipette to keep the tubule end in position. DIC image and fluorescence overlay are shown. (B) Summary of PGE2 biosensor responses. Fold change in Fluo-4/Fura Red fluorescence ratio is shown as index of PGE2 release. Addition of 40 nM bafilomycin (baf) to the bathing solution caused elevation in HEK-EP1 biosensor cell calcium indicating luminal PGE2 release. The effects of bafilomycin were prevented by the addition of the purinergic (ATP) receptor blocker suramin (50 μM) to the tubular perfusate. Similarly, the selective PGE2 EP1 receptor inhibitor SC51322 (SC; 10 μM) added to the luminal perfusate blocked bafilomycin-induced biosensor responses indicating PGE2 specificity. Addition of the ATP scavenger apyrase (50 U/ml) to the tubular perfusate also abolished PGE2 biosensor responses consistent with its dependence on luminal ATP release. *P < 0.05 bafilomycin vs. baseline (ctrl). Numbers per group are indicated in parentheses. (C and D) Fluorescence imaging of bafilomycin-induced purinergic calcium signaling in the isolated microperfused CCD. CCDs were perfusion-loaded with Fluo-4 and Fura Red. (C) Gradient pseudocolor images show CCD [Ca2+]i levels before (left) and after (right) addition of 40 nM bafilomycin to bathing solution. Bafilomycin caused significant elevations in CCD [Ca2+]i, most significantly in ICs, which were identified based on anatomical considerations (lower cell density and higher cell volume compared with PCs). (D) Summary of bafilomycin-induced changes in CCD [Ca2+]i. The purinergic (ATP) receptor blocker suramin added to the tubular perfusate (50 μM) abolished the effects of bafilomycin. *P < 0.05 bafilomycin vs. bafilomycin and suramin; n = 5/group.