Abstract
In skin-photosensitization studies on guinea-pigs benzanthrone induced significant erythema and oedema, depending upon the doses both of benzanthrone and of sunlight or artificially simulated UVA radiation. Maximum sensitization and delayed tanning response on the guinea-pig skin were observed 24-36 hr after irradiation. Photosensitized benzanthrone was found to produce significant amounts of singlet oxygen in vitro, as assessed by the bleaching of N,N-dimethyl-p-nitrosoaniline. As with haematoporphyrin and rose bengal, both of which are potent generators of singlet oxygen, the production of singlet oxygen by benzanthrone was dependent on both the concentration of the test chemical and the dose of solar radiation. Benzanthrone also produced a significant yield of superoxide anion radicals on exposure to simulated solar radiation or sunlight. Photosensitized benzanthrone induced photohaemolysis of rat erythrocytes and lipid peroxidation of erythrocyte ghosts, in vitro, probably largely through involvement of singlet oxygen (1O2). The rate of lipid peroxidation by photosensitized benzanthrone was inhibited by 64-80% with 1,4-diazabicyclo(2,2,2)octane and sodium azide, 15% with superoxide dismutase but was not affected by mannitol and sodium benzoate. Equimolar concentrations of haematoporphyrin and rose bengal also produced considerable photohaemolysis of erythrocytes and lipid peroxidation in erythrocyte ghosts; in both cases rose bengal was the most active and benzanthrone the least active of the three compounds.
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