Study gives insight into mechanism of body's regulation of salt balance

The body's capacity to keep a proper sodium balance, which is essential for determining blood pressure, is greatly influenced by the kidney. Many common diseases, including as hypertension, heart disease, and stroke, are influenced by imbalances in sodium, and these diseases can develop and advance.

Na/K-ATPase (NKA) is the enzymatic machinery that drives absorption of sodium along the renal proximal tubule. As such, it makes quite an unlikely candidate as a molecular counteractor of sodium absorption. In contrast, the Xie model for NKA receptor/signaling, named for the late Zijian Xie, Ph.D., predicts that NKA has evolved as the perfect molecular entity to sense intracellular sodium and coordinate the cellular response to temper absorption and maintain a steady delivery to the distal tubule.

Using gene targeting in cells and mice to test the respective contributions of NKA signaling and ion pumping to the overall regulation of renal sodium reabsorption, the study revealed that NKA signaling is functionally dominant over NKA ion pumping in the control of renal sodium reabsorption, according to new research published earlier this month in the FASEB journal, which ranks among the top biology journals in the world.

"This paper represents a major advance and a paradigm shift in renal physiology/mammalian salt handling," said Sandrine Pierre, Ph.D., interim director of the Marshall Institute for Interdisciplinary Research and the corresponding author on the study. "To date, it is the most tangible proof of the validity and physiological significance of the Xie model for sodium pump signaling."

Expertise in renal physiology and genetic approaches in experimental models to evaluate the non-classical Na/K-ATPase receptor function was provided by a cross-departmental team of investigators from the Marshall Institute for Interdisciplinary Research (MIIR) and the Joan C. Edwards School of Medicine. Xie, a pioneer of NKA non-ion pumping function, was a driving force behind this project from its inception.

"Developing the first genetic mouse model targeting NKA in renal proximal tubule cells has allowed us to unmask the dual antagonistic roles of NKA in renal Na+ and water reabsorption," said Shreya Mukherji, Ph.D., a scientist in the rare disease DDU at Takeda Pharmaceuticals U.S.A., Inc. and first author on the study, who conducted major portions of this research as a biomedical graduate student at Marshall University. "However, this is just a stepping stone. Using similar approaches, our group and others will likely dissect new regulatory networks and identify new targets in the management of hypertensive disorders and other highly prevalent chronic conditions." (ANI)