Evaluation of a nuclear magnetic resonance technique for the study of water exchange through erythrocyte membranes in normal and pathological subjects

Abstract

A critical evaluation has been performed of a NMR technique for the investigation of the water exchange time through erythrocyte membranes, based on doping with a paramagnetic salt. The conclusions are the following: 1. 1. The preparation of the samples for the NMR measurement plays an essential role in obtaining precise and reproducible values of the water exchange time through erythrocyte membranes. A method for optimum mixing of the whole blood with the doping solution is described. The values of the relaxation times of erythrocyte water protons obtained by using this method were reproducible to an accuracy ranging between 2%–6%. 2. 2. The theoretical basis of the method has been evaluated; the equations that should be employed for the calculation of the water exchange time are discussed. 3. 3. The water exchange time through normal erythrocyte membranes is 6.0 ± 0.5 ms . This value is not influenced by the presence of the doping paramagnetic solution; determinations by atomic absorption spectroscopy showed no significant penetration of the Mn 2+ into red blood cells. 4. 4. The temperature dependence of the water exchange time through the erythrocyte membranes is characterised by values of the apparent activation energy ranging between 6 and 8 kcal/mol. These values are similar to the activation energies of the molecular rotational motion or of the diffusion of water in mono- or submonolayers of adsorbed water. 5. 5. It has been found that the exchange time of water through erythrocyte membranes increased by 13–55% in patients with certain diseases such as Gaucher's disease, essential hyperlipemia, obstructive jaundice, chronic hepatitis, nephrotic syndrome. 6. 6. Our findings suggest that the NMR doping method is potentially useful for further studies of the physiology and pathology of erythrocyte water permeability.