Effect of Ethanol on the Radiation Sensitivity of Human Hemoglobin

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Abstract
Radiation sensitivity of oxy-, deoxy- and methemoglobin (HbO2, Hb2+ and MetHb) [from human Hb] in water solutions containing 0.2 M ethanol and in ethanol-free solutions was compared. Radiation sensitivity was estimated on the basis of changes in absorbance at the Soret band (.lambda. = 430 nm for Hb2+), changes in the absorbance ratio A505/A563 determined after conversion of irradiated preparations to MetHb, and changes in the value of parameters describing the reaction of Hb oxygenation. The presence of ethanol in irradiated preparations diminished protein destruction. The protection coefficient .vphi. of Hb by ethanol (ratio of a change in the absence of ethanol to that in its presence) calculated from changes in absorbance at the Soret band equaled .apprx. 1.5 at a 4-Mrad dose in all cases except MetHb irradiated in air for which .vphi. was much higher (.apprx. 3.2). The protection coefficient .vphi. calculated from D37 [mean inactivation dose] values for changes in A505/A563 equaled 2.2 for HbO2 and 2.8 for MetHb for preparations irradiated in air; .vphi.'' = 1.7 for Hb2+ and 1.8 for MetHb for preparations irradiated under Ar. On the basis of these results, the role of OH radicals and O2 in the radiation damage of Hb is discussed.