Evidence for a Change in the Fluidity of Erythrocyte Membranes Following X Irradiation by Measurement of Pyrene Excimer Fluorescence

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Abstract
The changes in the fluidity of sheep erythrocyte membranes following X-irradiation were investigated with the aid of a fluorescent aromatic hydrocarbon, pyrene. Pyrene excimer fluorescence is based upon the microviscosity dependence of the lateral diffusion rate of the probe in the membrane plane. The lateral diffusion rate obtained by this fluorescence technique can provide valuable information about the fluidity of the membrane environment of the probe. The excimer/monomer ratio, a parameter of the lateral diffusion rate, of pyrene bound to erythrocyte membranes irradiated with X-rays was higher than in unirradiated membranes. This effect was observable when 100 R were given to the membranes. The fluorescence polarization of membrane-bound pyrene decreased in X-irradiated membranes. X-irradiation apparently can induce an increase in the fluidity of the hydroxycarbon regions of the membranes.