The physiological and molecular mechanisms to maintain water and salt homeostasis in response to high salt intake in Mon
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ORIGINAL PAPER
The physiological and molecular mechanisms to maintain water and salt homeostasis in response to high salt intake in Mongolian gerbils (Meriones unguiculatus) Zahra Nouri1,2 · Xue‑Ying Zhang1,2 · De‑Hua Wang1,2 Received: 22 October 2019 / Revised: 29 May 2020 / Accepted: 7 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Desert rodents are faced with many challenges such as high dietary salt in their natural habitats and they have evolved abilities to conserve water and tolerate salt. However, the physiological and molecular mechanisms involved in water and salt balances in desert rodents are unknown. We hypothesized that desert rodents regulated water and salt balances by altering the expression of AQP2 and α-ENaC in the kidney. Mongolian gerbils (Meriones unguiculatus), a desert species, were acclimated to drinking water with different salt contents: (0, control; 4% NaCl, moderate salt, MS; 8% NaCl, high salt, HS) for 4 weeks. The gerbils drinking salty water had lower body mass, food intake, water intake, metabolic water production and urine volume. The HS gerbils increased the expression of arginine vasopressin (AVP) in the hypothalamus, and also enhanced the expression of AQP2 and cAMP/PKA/CREB signaling pathway in the kidney. In addition, these gerbils reduced serum aldosterone levels and α-ENaC expression in the kidney. Creatinine clearance was lower in the HS group than that in the control group, but serum and urine creatinine levels did not change. These data indicate that desert rodents rely on AVP-dependent upregulation of AQP2 and aldosterone-dependent downregulation of α-ENaC in the kidney to promote water reabsorption and sodium excretion under high salt intake. Keywords Aquaporin 2 (AQP2) · α-ENaC · Arginine vasopressin (AVP) · Mongolian gerbils (Meriones unguiculatus) · Salty water Abbreviations AQP2 Aquaporin 2 AVP Arginine vasopressin CREB cAMP-responsive element CRE-binding protein ENaC Epithelial sodium channel EWL Evaporative water loss HS High-salt group MR Mineralocorticoid receptors MS Moderate-salt group Communicated by Noga Kronfeld-Schor. * Xue‑Ying Zhang [email protected] * De‑Hua Wang [email protected] 1
State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
2
PKA Protein kinase A PVN Paraventricular nucleus RMR Resting metabolic rate RMT Relative medullary thickness RU Relative units SON Superoptic nucleus
Introduction Desert rodents have evolved multiple strategies, including morphological, behavioral, physiological, and ecological responses to adapt to the harsh environments (Bozinovic and Contreras 1990). In particular, they are faced with the necessity of water conservation and salt toleration in their natural habitats (Degen 1997; Schwimmer and Haim 2009). Desert rodents usually inhabit areas that conta
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