Independence of water and solute pathways in human RBCs

We have investigated the permeability of the human red blood cell to four di-hydroxy alcohols, 1,2PD (1,2 propanediol), 1,3PD (1.3 propanediol), 1,4BD (1,4 butanediol), and 2,3BD (2,3 butanediol), and to water by using a recently developed ESR stopped-flow method which is free from artifacts found in light scattering methods. Numerical solutions of the Kedem-Katchalsky equations fit to experimental data yielded the following permeability coefficients: P_1,2PD = 3.17 × 10^–5 cm sec^–1, p_1,3pd = 1.75 × 10^–5 cm sec^–1, P_1,4BD = 2.05 × 10⁵ cm sec^–1, P_2,3BD = 7.32 × 10^–5 cm sec^–1. Reflection coefficients () were evaluated by comparing data fit with assumed values of = 0.6,0.8 and 1.0. In all four cases the best fit was obtained with = 1.0. Treatment of cells with PCMBS (para-chloro mercuri-benzenesulfonate) was followed by a large (> 10-fold) decrease in water permeability with virtually no change in alcohol permeability. We conclude that these alcohols do not permeate the water channels to any significant extent, and discuss some of the problems in light scattering measurements of reflection coefficients that could lead to erroneous values for .We would like to thank Professor Lenore W. Yousef (Dept. of Biology, California State Univ., Fresno) for valuable discussions and critical comments. We thank Lidia Mannuzzu for measurements of ESR spectra in the presence and absence of alcohol. We are also indebted to Kate Van Fossen for her dedicated technical support. This work was supported by NIH grant No. HL-20985.