Glucose transport in human erythrocytes measured using 13C NMR spin transfer

We present the results of a new NMR-based procedure for measuring the fast transmembrane exchange of D-[1-13C]glucose in human erythrocytes. The method relies on different rates of exchange between the alpha- and beta-anomers of glucose inside and outside the cells; the rate outside the cells is greatly increased by the addition of mutarotase to the suspension. Theory is developed to describe nuclear-spin transfer in the present system and is used to analyse the data to yield estimates of transmembrane-exchange rate constants and their statistical uncertainties. For a total glucose concentration of 25.5 mmol/l at 40 degrees C the first order efflux rate constants for the alpha- and beta-anomers were 1.20 +/- 0.40 s-1 and 0.71 +/- 0.30 s-1, respectively.