Phosphorus nuclear magnetic resonance study of the rat kidney in vivo.

We show that phosphorus nuclear magnetic resonance (31P-NMR) can be used to study the metabolic state of kidneys in live, anesthetized rats without the need for surgery. To localize signals from the kidney, we used a radiofrequency surface coil in conjunction with the magnetic field profiling technique that is used for "topical magnetic resonance," (TMR). Signals are observed from phosphorus-containing metabolites including ATP and inorganic phosphate, and under certain conditions intracellular pH can be estimated. We suggest that the ratio of free ATP to free ADP is higher than the estimates of 1.5 to 2.0 obtained from freeze-clamping studies. Because of the important roles that ATP, ADP, inorganic phosphate, and pH are believed to play in cellular metabolism, it seems that 31P-NMR could be a powerful clinical tool.