NMR-STUDIES OF DIFFUSIONAL WATER PERMEABILITY OF RED-BLOOD-CELLS FROMTHE ECHIDNA TACHYGLOSSUS-ACULEATUS

The diffusional water permeability (P-d) of the red blood cells (RBC) from echidna (Tachyglossus aculeatus) was measured by a Mn2+-doping H- 1 nuclear magnetic resonance (NMR) technique at 400 MHz. The values of P-d were relatively low: around 1.9 x 10(-3) cm/sec at 25 degrees C, 2.2 x 10(-3) cm/sec at 29.5 degrees C, 2.9 x 10(-3) cm/sec at 35.2 deg rees C, 3.2 x 10(-3) cm/sec at 37 degrees C, 3.9 x 10(-3) cm/sec at 40 .5 degrees C and 4.2 x 10(-3) cm/sec at 42 degrees C. In parallel with the low water permeability the activation energy for the diffusion pr ocess (E(a,d)) was relatively high, similar to 33 kJ/mol. The membrane polypeptide electrophoretic pattern of echidna RBC was compared with its human counterpart. The proteins migrating in bands 3 and 4.1 had l ower mobilities in echidna compared with human membranes. In the echid na RBC membranes band 4.1 was not split into 4.1a and 4.1b sub-bands. Glyceraldehyde 3-phosphate dehydrogenase (band 6) was markedly less in tense in echidna than in human RBC. The faint bands between 4.2 and 5 and in the band 7-8 region showed considerable differences between the two species. At low ionic strength the pattern of solubilization of p roteins from echidna RBC membranes was different from human membranes, with only a trace of band 4.1 protein extracted from the echidna RBC.