X-Ray-Induced Structural Changes in Erythrocyte Membranes Studied by Use of Fluorescent Probes

The structural changes in erythrocyte membranes caused by X irradiation were investigated with the aid of fluorescent probes. It was found that the fluorescence intensity of 1-anilino-8-naphthalene sulfonate (ANS) combined with X-irradiated membranes decreased as a function of the dose. The effect could be observed even when 100 R was given. The lowering of the quantum yield of ANS fluorescence in the irradiated membranes seemed to be the primary cause of the fluorescence decrease, as the amount of bound ANS was found to be only slightly decreased. The fluorescence decrease was not accompanied by a significant shift of the emission spectrum to a longer wavelength. In addition, the fluorescence polarization of bound ANS decreased in X-irradiated membranes, suggesting that the decrease in quantum yield of bound ANS might be due to the decrease in membrane microviscosity. Measurement of the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene incorporated into the membranes indicated that it also decreased with increasing X-ray doses. The changes in the dynamic properties of erythrocyte membranes caused by X irradiation were further confirmed. From these results it was concluded that X irradiation readily induces significant changes of erythrocyte membrane structure.