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Abstract
The radioprotective action of respiratory coenzymes on DNA-water solutions is studied after irradiation with a 60Co source. Coenzymes were used separately or in mixtures of their oxidized and reduced forms. The Dose relative factor (DRF) values evaluated by uv absorbancy measurements of DNA damage were high: 18.03 for the(NAD-FAD-quinone) mixture (a respiratory chain model); 14.91 for (quinone-hydroquinone) mixture; 14.46 for quinone; 14.27 for hydro-quinone; 12.49 for FAD; 7.21 for the (NAD-NADH) mixture; 6.48 for NADH and 3.79 for NAD. No parallelism was found between the DNA coenzymes strong interactions and their protective action, performed by overcoming the indirect radiation damage. Besides, uv irradiation studies give no support to protection through direct energy transfer processes from excited DNA to coenzymes. The high efficiency of the mixtures of oxidized-reduced respiratory coenzymes is discussed in terms of simultaneous and equivalent trapping of recombinable radicals. The high tolerance of these protectors in living cells is emphasized.