NMR Measurements of Intracellular Ions in Living Systems

Abstract

Nuclear magnetic resonance (NMR) provides a unique methodology for noninvasive physiological measurements in living systems. It allows a direct visualization of anatomical structure in 1 H magnetic resonance imaging and measurements of flow and intracellular metabolites in whole animals and humans, along with spectroscopic measurements of intracellular ions and metabolites in perfused tissue, organ and cell systems. This chapter focuses on the development and use of NMR techniques for the measurement of intracellular ions in living systems. The chapter covers the recent advances made in the measurement of intracellular ions in cell suspensions and in perfused tissue, organ, and cell systems. It also discusses the recent applications of 23 Na NMR. The most common NMR method for the study of intracellular sodium ions employs membrane–impermeable highly anionic hyperfine shift reagents. These paramagnetic reagents, because of their localization in the extracellular compartment and the short range of their paramagnetic effects, interact only with the extracellular sodium ions, shifting their resonance away from the largely unaffected intracellular resonance. This allows the direct observation of the intracellular 23 Na resonance, the intensity of which is proportional to the intracellular sodium ion concentration.