UV-irradiation potentiates the antimutagenicity of p-aminobenzoic and p-aminosalicylic acids in Salmonella typhimurium.

Abstract UV-irradiation (254 nm, 10 or 20 J/cm 2 ) of p -aminobenzoic acid (PABA) and p -aminosalicylic acid (NaPAS) potentiated their antimutagenicity towards N -methyl- N ′-nitrosoguanidine mutagenesis in Salmonella typhimurium . Their inhibitory action towards the formation of the mutagen N -methyl- N -nitrosourea from the nitrosation mixture of N -methylurea and nitrite was also increased by UV-irradiation. In contrast, UV-irradiated PABA exhibited no inhibitory effects towards the mutagenicity of sodium azide or 3-azidoglycerol. Neither PABA nor NaPAS nor their UV-irradiation products were themselves mutagenic in the Ames assay.