Unknown phosphate compounds in tail muscle of intact conscious newts by 31P NMR

Unknown phosphate resonances at 0 and -21.6 ppm have been identified in 31P NMR spectra of tail muscle of unanesthetized newts which do not correspond to known phosphate-bearing compounds in skeletal muscle cells. The concentrations of both unknowns decrease markedly during muscular activity and severe hypoxia (conditions associated with decreased intracellular pH and increased cellular levels of inorganic phosphate). The unknown at 0 ppm increases in concentration with imposition of moderate hypoxia. Our data suggest that these unknowns may be liable storage compounds for a high energy phosphate bond, and are involved in newt skeletal muscle phosphogen metabolism.