3-Aminobenzamide sensitizes cultured Chinese hamster cells with bromodeoxyuridine-substituted DNA to genetic damage induced by long-wave UV.

Chinese hamster cells, containing BrdUrd-substituted DNA, were irradiated in the presence of 3-aminobenzamide with short-wave UV, long-wave UV or X-rays and analyzed for induced SCEs or chromosomal aberrations. The data presented in this paper show that when BrdUrd-substituted cells are irradiated with lw-UV in the presence of 3-aminobenzamide, genetic damage is increased. Biochemical analysis shows that the molecular weight of BrdUrd-substituted DNA is reduced by this treatment. The sensitization is due to the combined action of lw-UV, incorporated BrdUrd and 3-aminobenzamide, without any involvement of inhibition of poly(ADP-ribose) synthetase. No potentiation occurs when cells are irradiated with X-rays and genetic damage is decreased when cells are irradiated with UV light of 254 nm in the presence of 3AB. This decrease coincides with a reduction in the amount of induced pyrimidine dimers, detected as T4 endonuclease-sensitive sites in DNA.