Hydrogen peroxide (H202) is an endogenous chemical that is toxic and had been reported to be weakly mutagenic. We have studied the mutagenicity of H202 in Salmonella and optimized the conditions for its detection. The newly constructed strain, SB1106+ gives a higher response than the standard mutagenicity testing strains TA97, TA100, TA102, or TA104. The mutagenic response will be correlated with the levels of catalase in the cells. An HPLC procedure for examining the DNA damage induced by H202 is being developed. Standards have been obtained or synthesized for major known oxygen-induced damaged bases (thymidine glycol; 8- hydroxydeoxyguanosine; 5-hydroxymethyldeoxyuridine), and the DNA extraction and purification procedures are being developed for the Salmonella cells. These procedures will be used to identify the pattern of damaged DNA bases induced by H202. Chemicals believed to cause mutation or damage DNA through the formation of oxygen radicals will be examined to determine whether H202 is an active intermediate or whether a different radical is the active product(s). This will be done by comparing the pattern of DNA damage with that produced by H202. Among the chemicals that will be examined are glutathione, cysteine, and other thiols that appear to be mutagenic via H202 formation, and metal ion complexes which are believed to produce active oxygen species.
