The characteristics of water diffusional permeability (P) of human red blood cells were studied on isolated erythrocytes by a doping nuclear magnetic resonance technique. In order to estimate the basal permeability the maximal inhibition of water diffusion was induced by exposure of red blood cells to p-chloromercuribenzene sulfonate (PCMBS) under various conditions (concentration, duration, temperature). The lowest values of P were around 0.7×10−3 cm s−1 at 10°C, 1.2×10−3 cm s−1 at 15°C, 1.4×10−3 cm s−1 at 20°C, 1.8×10−3 cm s−1 at 25°C, 2.1×10−3 cm s−1 at 30°C and 3.5×10−3 cm s−1 at 37°C. The mean value of the activation energy of water diffusion (Ea,d) was 25 kJ/mol for control and 43.7 kJ/mol for PCMBS-inhibited erythrocytes. The values of P and Ea,d obtained after induction of maximal inhibition of water diffusion by PCMBS can be taken as references for the basal permeability to water of the human red blood cell membrane.

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