Affiliation:
1. Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
2. Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
Abstract
Maintaining extracellular potassium (K+) within narrow limits, critical for membrane potential and excitability, is accomplished through the internal redistribution of K+ between extracellular fluid (ECF) and intracellular fluid (ICF) in concert with the regulation of renal K+ output to balance K+ intake. Here we present evidence from high-precision analyses of stable K+ isotopes in rats maintained on a control diet that the tissues and organs involved in the internal redistribution of K+ differ in their speed of K+ exchange with ECF and can be grouped into those that exchange K+ with ECF either rapidly or more slowly (“fast” and “slow” pools). After 10 days of K+ restriction, a compartmental analysis indicates that the sizes of the ICF K+ pools decreased but that this decrease in ICF K+ pools was not homogeneous, rather occurring only in the slow pool (15% decrease, p < 0.01), representing skeletal muscles, not in the fast pool. Furthermore, we find that the dietary K+ restriction is associated with a decline in the rate constants for K+ effluxes from both the “fast” and “slow” ICF pools (p < 0.05 for both). These results suggest that changes in unidentified transport pathways responsible for K+ efflux from ICF to ECF play an important role in buffering the internal redistribution of K+ between ICF and ECF during K+ restriction. Thus, the present study introduces novel stable isotope approaches to separately characterize heterogenous ICF K+ pools in vivo and assess K+ uptake by individual tissues, methods that provide key new tools to elucidate K+ homeostatic mechanisms in vivo.
Funder
National Institutes of Health
Reference25 articles.
1. Potassium homeostasis: Sensors, mediators, and targets;McDonough;Pflugers Arch.,2022
2. Potassium homeostasis—Physiology and pharmacology in a clinical context;Kettritz;Pharmacol. Ther.,2023
3. Physiology and Pathophysiology of Potassium Homeostasis: Core Curriculum 2019;Palmer;Am. J. Kidney Dis.,2019
4. Potassium recycling;Jamison;Kidney Int.,1987
5. Seldin, D.W., and Giebisch, G. (1989). Potassium intoxication: Pathogenesis and treatment. The Regulation of Potassium Balance, Raven.