THE ROLE OF GLUTATHIONE IN PROTECTION AGAINST DNA-DAMAGE INDUCED BY RIFAMYCIN SV AND COPPER(II) IONS

Incubation of calf thymus DNA in the presence of rifamycin SV induces a decrease in the absorbance of DNA at 260 nm. The effect, was found t o be proportional to the antibiotic concentration and enhanced by copp er(II) ions. In the presence of rifamycin SV and copper(II), a signifi cant increase in thiobarbituric acid-reactive (TBA-reactive) material is also observed. This effect is inhibited to different degrees by the following antioxidants: catalase 77%; thiourea 72%; glutathione (GSH) 62%; ethanol 52%; and DMSO 34%, suggesting that both hydrogen peroxid e (H2O2) and hydroxyl radicals (OH.) are involved in DNA damage. Rifam ycin SV-copper(II) mixtures were also found to induce the production o f peroxidation material from deoxyribose and, in this case, glutathion e and ethanol were the most effective antioxidant substrates with inhi bition rates of 91% and 88% respectively Electrophoretic studies show that calf thymus DNA becomes damaged after 20 min. incubation in the p resence of both agents together and that the damaged fragments run wit h migration rates similar to those obtained by the metal chelating age nt 1, 10-phenanthroline. Normal DNA electrophoretic pattern was found to be preserved by catalase, and GSH at physiological concentrations a nd by thiourea. No protection is observed in the presence of ethanol o r DMSO. The results obtained indicate the involvement of different rea ctive species in the degradation process of DNA due to rifamycin SV-co pper(II) complex and emphasize the role of reduced glutathione as an o xygen free radical scavenger.