The effects of caffeine on the mutation frequency at the adenine phosphoribosyl transferase locus in Chinese hamster ovary cells exposed to ultraviolet light
Cesario, Rosemary Margaret
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Two Chinese hamster ovary (CHO) cell lines, wild type AA8 and excision repair deficient UV5, were exposed to ultraviolet light (UV) and then treated for four hours with 2, 4, or 8 mM caffeine. Studies on cell survival, rate of DNA synthesis, and mutation frequency were performed. The survival of UV5 cells decreased with post-UV caffeine treatment. Survival of AA8 cells was not affected by the presence of caffeine for four hours after UV exposure. An attenuation of the UV-induced depression in DNA synthesis was observed in UV5 cells treated with 4 mM caffeine after UV exposure, but no effect was shown on the AA8 cell line. Mutation studies on the adenine phosphoribosyl transferase (APRT) locus were also performed. In UV5 cells there was an increase in mutants per survivor with a 2 J/m^ or higher fluence exposure after caffeine treatment. In AA8 cells no consistant change in mutation rate was noted following caffeine treatment after UV exposure. The presence or absence of an excision repair system appears to determine whether cell survival, DNA synthesis and mutation frequency are effected by post-UV cafeine treatment. This suggests a possible activation by caffeine of an "error prone" repair system or enhancement of UV-induced lesion bypass in DNA.