Loss of photoreactivation in UV-irradiated cultured fish cells under different conditions

CAF-MM1 cells derived from a goldfish have photoreactivability for the damage induced by ultraviolet light. When UV-irradiated cells were incubated in the dark at 260C, the longest interval in which photoreactivation (PR) was observed, measured by colony formation technique, was about 30h after the UV irradiation. However, if the cells were incubated at 200C, the effective time was prolonged. Since each time appeared to correspond to the doubling time of the cells at each temperature, the loss of photoreactivability is suggested to be closely related to cell growth or progression of cell cycle. The loss of PR was not observed in the cells held in confluence up to 48h after UV irradiation. Photoreactivating enzyme in growing CAF-MM1 cells incubated in the dark for 24h after UV irradiation was shown to be active, so that it is not possible that the cause of the loss of PR is change in the activity of photoreactivating enzyme. (author)