摘要：Under normal conditions, high sodium (Na
+) in extracellular (Na
+
e) and blood (Na
+
b) compartments and low Na
+ in intracellular milieu (Na
+
i) produce strong transmembrane (ΔNa
+
mem) and weak transendothelial (ΔNa
+
end) gradients respectively, and these manifest the cell membrane potential (
V
m
) as well as blood–brain barrier (BBB) integrity. We developed a sodium (
23Na) magnetic resonance spectroscopic imaging (MRSI) method using an intravenously-administered paramagnetic polyanionic agent to measure ΔNa
+
mem and ΔNa
+
end. In vitro
23Na-MRSI established that the
23Na signal is intensely shifted by the agent compared to other biological factors (e.g., pH and temperature). In vivo
23Na-MRSI showed Na
+
i remained unshifted and Na
+
b was more shifted than Na
+
e, and these together revealed weakened ΔNa
+
mem and enhanced ΔNa
+
end in rat gliomas (vs. normal tissue). Compared to normal tissue, RG2 and U87 tumors maintained weakened ΔNa
+
mem (i.e., depolarized
V
m
) implying an aggressive state for proliferation, whereas RG2 tumors displayed elevated ∆Na
+
end suggesting altered BBB integrity. We anticipate that
23Na-MRSI will allow biomedical explorations of perturbed Na
+ homeostasis in vivo.
