The kidneys maintain constant levels of K+ in the plasma and extracellular fluids by matching urinary excretion of the ions to dietary intake. This process involves a complex signaling system through which the renal tubular cells interact with the plasma K+ concentration and perhaps also with the gut and endocrine organs. However the nature of this system is not well understood. We will examine how this process works by assessing the function of K+ channels in the apical membrane of the rat connecting tubule and collecting duct. These channels are thought to be the key pathway through which K+ is secreted into the urine. We will measure the overall activity of the channels using electrophysiological techniques, the total abundance of channels using immunoblotting, and the amount of protein in the apical membrane using a biotinylation approach for labeling proteins at the cell surface. We will correlate these parameters with parallel measurements of Na channel activity and NaCl-cotransporter expression. We will test the hypothesis that the serine/threonine kinase SGK1 plays an important role in the modulation of these processes and of renal K excretion. We will also assess the ability of insulin to acutely influence K+ transport in distal nephron segments. Finally, we will examine the interactions between these channels and intracellular Mg2+, changes of which may be important in pathological conditions involving Mg depletion or wasting.

Public Health Relevance

Proper function of the kidneys is essential for maintaining the optimal concentration of potassium ions in the body fluids. Concentrations that are either too high or two low lead to cardiac arrhythmias or in the extreme case to cardiac arrest. We will study how the kidneys keep the levels of this ion constant by measuring the amount and the function of proteins at the surface of kidney cells that allow potassium to be transported into the urine, where it is eventually excreted from the body. Understanding how this process works and how it changes in response to different amounts of potassium in the diet will help in the management and treatment of patients with hypokalemia and hyperkalemia.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Cellular and Molecular Biology of the Kidney Study Section (CMBK)
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Ketchum, Christian J
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Weill Medical College of Cornell University
Schools of Medicine
New York
United States
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Yang, Lei; Frindt, Gustavo; Lang, Florian et al. (2017) SGK1-dependent ENaC processing and trafficking in mice with high dietary K intake and elevated aldosterone. Am J Physiol Renal Physiol 312:F65-F76
Frindt, Gustavo; Gravotta, Diego; Palmer, Lawrence G (2016) Regulation of ENaC trafficking in rat kidney. J Gen Physiol 147:217-27
Frindt, Gustavo; Palmer, Lawrence G (2015) Acute effects of aldosterone on the epithelial Na channel in rat kidney. Am J Physiol Renal Physiol 308:F572-8
Palmer, Lawrence G; Schnermann, J├╝rgen (2015) Integrated control of Na transport along the nephron. Clin J Am Soc Nephrol 10:676-87
Patel, Ankit B; Yang, Lei; Deng, Su et al. (2014) Feedback inhibition of ENaC: acute and chronic mechanisms. Channels (Austin) 8:444-51
Yang, Lei; Palmer, Lawrence G (2014) Ion conduction and selectivity in acid-sensing ion channel 1. J Gen Physiol 144:245-55
Frindt, Gustavo; Li, Hui; Sackin, Henry et al. (2013) Inhibition of ROMK channels by low extracellular K+ and oxidative stress. Am J Physiol Renal Physiol 305:F208-15
Yang, Lei; Edvinsson, Johan; Sackin, Henry et al. (2012) Ion selectivity and current saturation in inward-rectifier K+ channels. J Gen Physiol 139:145-57
Yang, Lei; Edvinsson, Johan; Palmer, Lawrence G (2012) Interactions of external K+ and internal blockers in a weak inward-rectifier K+ channel. J Gen Physiol 140:529-40
Sackin, Henry; Nanazashvili, Mikheil; Li, Hui et al. (2012) Residues at the outer mouth of Kir1.1 determine K-dependent gating. Biophys J 102:2742-50

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