Rubidium transport in human erythrocyte suspensions monitored by 87Rb NMR with aqueous chemical shift reagents.

Dysprosium(III) triethylenetraamine-N,N,N',N",N"',N"'-hexaacetic acid (DyTTHA3-) was used as an aqueous chemical shift reagent in conjunction with high-resolution nuclear magnetic resonance (NMR) spectroscopy to monitor 87-rubidium (87Rb+) transport in human erythrocyte suspensions. NMR spectra demonstrated two resonances which were assigned to the intra- and extracellular compartments of the erythrocyte suspension. Uptake of 87Rb+ was shown to proceed via the [Na,K]-ATPase dependent pump as evidenced by the inhibition of uptake in the presence of ouabain. The steady state intra- to extracellular concentration ratio of 87Rb was 3.00 and 1.13 in the absence and presence of ouabain, respectively. The rate of uptake of 87Rb+ in the absence and presence of ouabain was found to be 1.3 and 0.5 mmol Rb+/L erythrocytes/h at 18 mM Rb+, respectively. Data are also presented which indicate that the intracellular component of 87Rb is less than 100% NMR visible.