Pulse nuclear magnetic resonance measurements of water exchange across the erythrocyte membrane employing a low Mn concentration

• Published in: Biophysical journal 1979-03, Vol.25 (3), p.389-406
• Main Authors: Pirkle, J.L., Ashley, D.L., Goldstein, J.H.
• Format: Article
• Language: English
• Subjects: Body Water - metabolism; Erythrocyte Membrane - drug effects; Erythrocyte Membrane - metabolism; Erythrocytes - metabolism; Hematocrit; Humans; Magnetic Resonance Spectroscopy; Manganese - pharmacology; Mathematics; Models, Biological
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/S0006-3495(79)85311-4

A simple, precise, and rapid pulse nuclear magnetic resonance technique for measuring the rate of water exchange across the erythrocyte membrane is presented. The technique is based upon the nonlinear fit of Carr-Purcell-Meiboom-Gill (CPMG) transverse relaxation time data of blood doped with 1.7 mM MnCl2 to the general two-compartment exchange condition. Previous approaches using CPMG data required high MnCl2 concentrations (25–53 nM), shown in this work to induce systematic errors ranging from 35 to 45%. At 23 degrees C the average residence time of a water molecule inside the erythrocyte (tau a) is 21.0 +/- 0.6 ms (SE). The Arrhenius plot for water exchange is linear over the range of 3 degrees - 37 degrees C and th Arrhenius activation energy is 4.79 +/- 0.03 kcal (SE). This value does not differ significantly from the energy required for bulk water flow. Results are compared with previous determinations, and sources of systematic error in tau a and the activation energy are evaluated.