Comparative nuclear magnetic resonance studies of diffusional water permeability of red blood cells from sheep and cow

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1. 1. The diffusional water permeability ( p) of sheep and cow red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulfonate (PCMBS). 2. 2. There were no significant differences in the water permeability of sheep and cow RBCs, the values of p being around 3 × 10 −3 cm/sec at 20°C and 5 × 10 −3 cm/sec at 37°C. 3. 3. Systematic studies of the effects of PCMBS on water diffusion indicated that in both species the maximal inhibition is reached in 60–90 min at 37°C with 1 mM PCMBS. 4. 4. The degree of inhibition increased as the temperature of measurement decreased, regardless of PCMBS concentration and incubation time. 5. 5. The values of maximal inhibition ranged from 60–70% at 20°C to 50–60 at 37°C in the case of sheep RBCs, and from 45–55% at 20°C to 40–50% at 37°C in the case of cow RBCs. 6. 6. The basal permeability to water of sheep RBCs was estimated as 1.0 × 10 −3 cm/sec at 20°C and 2.2 × 10 −3 cm/sec at 37°C, and that of cow RBCs as 1.6 × 10 −3 cm/sec at 20°C and 2.7 × 10 −3 cm/sec at 37°C. 7. 7. In both species the activation energy of water diffusion was around 23 kJ/mol in control cells and reached values of around 30 kJ/mol after incubation with PCMBS in conditions of maximal inhibition of water diffusion. 8. 8. The membrane polypeptide electrophoretic patterns of sheep and cow RBCs have been compared with their human counterparts. 9. 9. The proteins migrating in bands 1 and 2 (corresponding to spectrins) and in band 6 (glyceraldehyde-3-phosphate dehydrogenase) were less abundant in sheep and cow RBCs compared to human RBCs. 10. 10. There were also differences between sheep and cow RBC membrane proteins. 11. 11. Proteins in bands 2.1–2.3 (ankyrins) and band 3 were decreased in cow RBC membrane. 12. 12. These changes in membrane proteins did not seem to correlate with significant differences in the diffusional permeability to water of RBCs in these species.