Molecular Pharmacology, Vol 13, 435-441, Copyright © 1977 by the American Society for Pharmacology and Experimental Therapeutics

Effects of Low Concentrations of Ethanol on the Fluidity of Spin-Labeled Erythrocyte and Brain Membranes

¹ Department of Pharmacology, Stanford University School of Medicine, Stanford, California 94305

The effects of ethanol on membrane fluidity at 37° have been assessed by a sensitive electron paramagnetic resonance technique. Erythrocyte and brain membranes from DBA/2J mice were spin-labeled with 5-doxylstearic acid (N-oxyl-4',4'-dimethyloxazolidine derivative of 5-ketostearic acid). The molecular motion of the spin label was measured from the EPR spectrum by determining the order parameter S, an index of membrane fluidity. The fluidity of both erythrocyte and synaptosomal membranes was greater than that of myelin but less than that of mitochondrial membranes. The addition of low concentrations (0.02 or 0.04 M) of ethanol in vitro increased fluidity in erythrocyte, mitochondrial, and synaptosomal membranes. This fluidizing effect of ethanol was dose-related up to 0.35 M in all the membranes except myelin. These data suggest that nonlethal concentrations of ethanol may increase membrane fluidity in vivo.

Note:
ACKNOWLEDGMENTS We thank Drs. Ellis Cohen and James Trudell, Department of Anesthesiology, for extensive use of their equipment for the EPR recordings. We also thank Dr. Trudell for many helpful discussions.

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