In vivo 31P NMR spectra of rat submandibular glands were obtained. The glands were exposed, leaving the neurovascular system intact, and placed in a solenoidal coil. Resonances of nine phosphate metabolites were identified in the spectra and metabolite concentrations were estimated from the corresponding integrals ([ATP] = 3.4 +/- 0.7 mM). Tissue pH, as deduced from the chemical shift of the inorganic phosphate resonance, was 7.26 (+/- 0.07). T1 relaxation times of ATP, phosphocreatine, inorganic phosphate, and phosphomonoester 31P spin systems were examined. The effect of hypoxia was followed as a function of time. 31P NMR spectra of the glands have also been obtained noninvasively by the use of a surface coil, adapted to the dimensions of the glands, and depth pulses.