A 31P NMR study on uptake and metabolism of hexose monophosphates in rat diaphragm muscle.

Phosphorus nuclear magnetic resonance spectroscopy was used to study uptake and metabolic conversion of glycolytic intermediates in rat diaphragm muscles. The resonances of several phosphorus-containing metabolites were identified in the intact tissues and in their ethanolic extracts. Experiments on muscles preincubated with glucose 6-phosphate or glucose 1-phosphate indicated that: 1) both substrates penetrate into the tissue and actively participate in glycolytic reactions; 2) glucose 1-phosphate is completely converted into other metabolites, including glucose 6-phosphate and its products; 3) preincubation with either hexose monophosphate in the presence or in the absence of insulin produced the same set of phosphorylated metabolites. Addition of insulin to preincubation media induced a conspicuous spread of chemical shifts in the band arising from phosphorylated sugars in tissues incubated with glucose 1-phosphate but not in those treated with glucose 6-phosphate. The different responses to insulin exhibited by the 31P n.m.r. spectral profiles of tissues incubated with the two substrates substantiate the hypothesis that glucose 6-phosphate and its products may undergo their metabolic conversions in the tissue along distinct intracellular enzymatic pathways, on which insulin would exert different regulatory effects. This study indicates that 31P n.m.r. may provide a useful approach to the elucidation of metabolic processes involving sugar phosphates in intact tissues.