Relation of UV Dose to Antioxidant Modification of Photocarcinogenesis

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Abstract
Studies were undertaken to examine the influence of various levels of ultraviolet light (UV) on the anticarcinogenic properties of antioxidants. Six groups of female, hairless mice were subjected to daily irradiation until pairs of groups had received a cumulative dose of 21.6, 31.6, and 44 sunburn units respectively. Control groups, at each level of UV, were maintained on a closed formula ration. Experimental groups received the same ration supplemented with a 2% (w/w) antioxidant mixture. Tumor latency, expressed as median time to tumor development, was significantly greater for antioxidant-supplemented animals at all three doses than for similarly UV-dosed controls. The inhibitory response to antioxidants decreased with increasing UV dose. Likewise, antioxidant-supplemented animals, at all three UV doses, exhibited a significantly fewer number of tumors per animal. In the control groups, only the lowest UV dose, when compared to the two higher doses, demonstrated a longer tumor latency period. On the other hand, tumor multiplicity for control animals appeared to be a more sensitive response to UV dose. It is concluded that UV dose influences the degree of photoprotection afforded by antioxidants and is an important experimental parameter to be considered when evaluating potential chemopre-ventive agents.