Quantitation of intracellular [Na+] in vivo by using TmDOTP5− as an NMR shift reagent and extracellular marker

Abstract

A method is presented to measure the absolute concentration of intracellular Na+([Na+]i) in vivo by using interleaved 23Na- and 31P-nuclear magnetic resonance (NMR) spectroscopy and TmDOTP5− as shift reagent and chemical marker of tissue extracellular space (ECS). The technique was used to determine [Na+]iand relative ECS in livers of control rats (21 ± 3 and 0.11 ± 0.02 mM, respectively) and in rats exposed to carbon tetrachloride (103 ± 29 and 0.23 ± 0.03 mM, respectively). The NMR measurements were confirmed independently on excised tissue samples by using atomic absorption spectroscopy. The results confirm that TmDOTP5− can be used as a combined cation shift reagent and ECS marker, thereby allowing quantitation of [Na+]iin vivo by NMR.