(727.8) Adaptation to High-Salt Diet Requires H,K-ATPase Type 2 Dependent NaCl Secretion

Poster Board Number: E201

Lydie Cheval (Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire de Physiologie Rénale et Tubulopathies, F-75006 Paris, France, CNRS ERL 8228 – Unité Métabolisme et Physiologie Rénale, F-75006, Paris, France), Samia Lasaad (Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire de Physiologie Rénale et Tubulopathies, F-75006 Paris, France, CNRS ERL 8228 – Unité Métabolisme et Physiologie Rénale, F-75006, Paris, France), Chloé Rafael (Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire de Physiologie Rénale et Tubulopathies, F-75006 Paris, France, CNRS ERL 8228 – Unité Métabolisme et Physiologie Rénale, F-75006, Paris, France), Luciana Morla (Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire de Physiologie Rénale et Tubulopathies, F-75006 Paris, France, CNRS ERL 8228 – Unité Métabolisme et Physiologie Rénale, F-75006, Paris, France), Nicolas Picard (Laboratory of Tissue Biology and Therapeutic Engineering, UMR 5305 CNRS, University Lyon 1, Lyon, F-69367, France), Gilles Crambert (Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire de Physiologie Rénale et Tubulopathies, F-75006 Paris, France, CNRS ERL 8228 – Unité Métabolisme et Physiologie Rénale, F-75006, Paris, France)

Introduction: The kidney controls the extracellular volume and the blood pressure because of its ability to excrete efficiently Na+ and Cl- ions. These last decades in Western countries the consumption of salt has dramatically increase and the question arises as to how the kidney adapts to this chronic situation. Up to now, the mechanisms described to excrete a large load of salt consist in the inhibition of Na+ reabsorption all along the nephron. We have recently identified a novel pathway that mediates the secretion of Na+ in the collecting duct (Morla, L. et al. 2016). This system involves A-type intercalated cells (AIC), NKCC1 and the H,K-ATPase type 2 (HKA2), which is known to be able to transport Na+. Here, we investigated the role of HKA2 in NaCl renal secretion, as well as the physiological relevance of this secretory pathway in vivo, in response to salt load.

Material and

Methods: C57BL6J mice wild type or knockout for the Atp12a gene (HKA2-KO) were used and placed under a control (NS) or high-Na+ (HS) diets for 3 days. Outer medullary collecting ducts (OMCD) of WT mice under NS or HS were isolated for RNAseq and RT-PCR analysis. Type A intercalated cells were isolated by FACS (following labelling with c-kit antibodies) from WT mice under NS or HS for RT-PCR analysis. The mice were also placed in metabolic cages for measurements of physiological parameters (food and water intakes, urine excretion, plasma parameters). Blood pressure was assessed by tail-cuffed measurement.

Results: The RNA seq analysis of OMCD revealed that, as expected, genes involved in Na+ reabsorption (ENaCa, SGK) are downregulated. However, we also observed that HS diet also leads to an increased expression of the Atp12a gene that encodes for the catalytic subunit of the HKA2 both in OMCD and ICA. To understand the role of the HKA2, we placed the HKA2-KO mice under high-salt diet and observed that those mice exhibit a salt loosing phenotype with low blood pressure that is due to a stronger down-regulation of NKCC2 than in WT in the same context. Therefore, the absence of HKA2 is over-compensated by the inhibition of a reabsorption pathway.

Conclusion: Altogether, these results demonstrate that the secretion of Na+ in OMCD is stimulated in response to high salt intake.

This study was supported by the Agence Nationale de la Recherche (ANR-21-CE14-0040-01) and by the Fondation pour la Recherche Mamp;eacute;dicale (FRM: DPC20171138949). S.L. is a PhD student supported by the Ministamp;egrave;re de lEnseignement Supamp;eacute;rieur, de la Recherche et de lInnovation (MESRI). C.R. is supported by grant from the fondation Lefoulon-Delalande.