Comparative nuclear magnetic resonance studies of diffusional water permeability of red blood cells from different Species. XI. Horses introduced to Australia and European horses (Equus caballus)

The diffusional water permeability (P-d) of red blood cells (RBCs) from hor ses introduced to Australia and from European horses was measured by a Mn2 doping nuclear magnetic resonance (NMR) technique. The values of P-d were similar to3.5 X 10(-3) cm/s at 25 degreesC, 4.1 x 10(-3) cm/s at 30 degrees C, 5.6 x 10(-3) cm/s at 37 degreesC and 6.3 x 10(-3) cm/s at 42 degreesC wi th no significant differences between the two strains of horse. Systematic studies on the effect of p-chloromercuribenzene sulphonate (PCMBS) on water diffusion indicated that the maximal inhibition (60%) was reached in 60 mi n at 22 degreesC with 1 mM PCMBS. The basal permeability to water was estim ated at 1.2 x 10(-3) cm/s at 25 degreesC, 1.7 x 10(-3) cm/s at 30 degreesC, 2.0 x 10(-3) cm/s at 37 degreesC and 2.7 x 10(-3) cm/s at 42 degreesC. The activation energy (E-a,E-d) of water diffusion was similar to 25 kJ/mol an d increased to similar to 39 kJ/mol after incubation with PCMBS, in conditi ons of maximal inhibition of water diffusion. The membrane protein electrop horetic pattern of horse RBCs was compared with its human counterpart. The horse RBC membranes had lower amounts of the proteins migrating as bands 4. 1 and 4.2 and higher amounts of the protein migrating as band 4.9, and band 6 (glyceraldehyde-3-phosphate dehydrogenase) was undetectable. A noteworth y feature was the appearance of considerable differences in protein migrati on distances in the region of bands 7 and 9, between horse and human membra nes.