Abstract
The 13C NMR spectrum of 13C-urea in a suspension of human red cells of reduced mean cell volume was observed to contain partially resolved resonances arising from the intra- and extracellular populations of the compound. It was shown that at 25 degrees C and a magnetic field strength of 9.4 T, the rate of exchange of urea between the intra- and extracellular populations was such that the NMR lineshape was sensitive to a change in the rate of 13C-urea exchange, induced either by the addition of the urea transport inhibitor phloretin, or by the addition of 12C-urea. Total lineshape analysis of 13C NMR spectra of 13C-urea in red cell suspensions containing different concentrations of 12C-urea resulted in a weighted mean estimate for the Km and Vmax for urea equilibrium exchange from three experiments of 44 +/- 18 mM and 3.1 +/- 0.6 x 10(-8) mol cm-2 s-1, respectively (the errors denote the weighted mean standard deviations). These estimates of Km and Vmax were significantly lower than previous values reported in the literature and determined using other techniques.
| Original language | English |
|---|---|
| Pages (from-to) | 207-16 |
| Number of pages | 10 |
| Journal | European biophysics journal : EBJ |
| Volume | 21 |
| Issue number | 3 |
| Publication status | Published - 1992 |
Keywords
- Adult
- Carbon Isotopes
- Cell Membrane Permeability
- Erythrocyte Membrane
- Humans
- Kinetics
- Magnetic Resonance Spectroscopy
- Mathematical Computing
- Spectrum Analysis
- Urea