Phosphorus-31 nuclear magnetic resonance studies of human red blood cells

Phosphorus-31 nuclear magnetic resonance spectroscopy is used to monitor the changes in the concentrations of 2,3-diphosphoglycerate and adenosine-5' triphosphate as a function of time and to measure the intracellular pH of normal and abnormal red blood cells in the presence of 25% oxygen, 5.6% carbon dioxide, and 69.4% nitrogen at 37 degrees C. Under these conditions, the intracellular pH values of normal AA, sickle SS, AS, SC, AC, and CC red cells are 7.24 +/- 0.07, 7.13 +/- 0.04, 7.15 +/- 0.03, 7.16 +/- 0.03, 7.24 +/- 0.05, and 7.14 +/- 0.03, respectively. The intracellular pH of SS red cells is about 0.1 pH unit more acidic than that of AA red cells. Time-dependent changes in the concentration of 2,3-diphosphoglycerate of normal human red cells show an initial lag phase, followed by a slow linear decrease. The duration of the initial lag phase decreases in the following order: AA approximately equal to AS approximately equal to AC greater than SC greater than SS approximately equal to CC red cells. The decay of 2,3-diphosphoglycerate is much faster in SS and CC red cells compared to other red cells studied. The time-dependent depletion of adenosine-5' triphosphate in these red cells is similar in nature to that of 2,3-diphosphoglycerate. The linewidths of 2-P and 3-P resonances of 2,3-diphosphoglycerate for fully oxygenated SS red cells are broader (approximately 20 Hz) than those for other red cells (approximately 10 Hz). However, the linewidths of 2-P and 3-P resonances of 2,3-diphosphoglycerate in the lysates of these red cells are narrower (approximately 4.5 Hz) than those in the intact red cells and are very similar in all types of red cells studied. The linewidths of the 31P resonances of adenosine-5' triphosphate are also similar (approximately 30-40 Hz) in all red cells studied. In addition, we have investigated the effect of carbamylation on the metabolism of 2,3-diphosphoglycerate and the intracellular pH in SS and AA red cells and have found that neither one is affected by this process. Our results provide further evidence that phosphorus-31 nuclear magnetic resonance spectroscopy offers a direct, non-invasive way to investigate the intracellular environment and the metabolism of phosphorylated metabolites in intact red blood cells.