In vivo P-NMR spectroscopy: muscle energy exchange in paramyotonia patients.

Using phosphorus nuclear magnetic resonance spectroscopy, we studied the muscle metabolism in four patients with paramyotonia congenita as reflected in the PC/Pi and PC/ATP ratios. At normal body temperature, all results were indistinguishable from controls. After cooling to 29 degrees C muscle temperature and a single 2-sec maximum contraction, the forearm muscles were stiff. At this stage, no decrease in the ATP content could be detected. In greater than 50% of the experiments with patients, an additional peak occurred transiently at the resonant frequency for monophosphates. After a working period at 29 degrees C muscle temperature, the paramyotonic muscles were paralyzed, but displayed spectra similar to those obtained at normal body temperature and full working capability. Intracellular pH was close to 7 in paramyotonic muscle under all conditions examined.