Stoichiometric Relationship between Na+ Ions Transported and Glucose Consumed in Human Erythrocytes: Bayesian Analysis of Na-23 and C-13 NMR Time Course Data

We examined the response of Na+,K+-ATPase (NKA) to monensin, a Na+ ionophore, with and without ouabain, an NKA inhibitor, in suspensions of human erythrocytes (red blood cells). A combination of C-13 and Na-23 NMR methods allowed the recording of intra- and extracellular Na+, and C-13-labeled glucose time courses. The net influx of Na+ and the consumption of glucose were measured with and without NKA inhibited by ouabain. A Bayesian analysis was used to determine probability distributions of the parameter values of a minimalist mathematical model of the kinetics involved, and then used to infer the rates of Na+ transported and glucose consumed. It was estimated that the numerical relationship between the number of Na+ ions transported by NKA per molecule of glucose consumed by a red blood cell was close to the ratio 6.0:1.0, agreeing with theoretical prediction.