Relationship of the Cell Cycle to Sunburn Cell Formation

— Relationship of the cell cycle to sunburn cell (SBC) formation was investigated in vivo. The number of SBC counted 24 h after UV irradiation was decreased by intradermal injection of chemicals which suppress cell proliferation, such as colchicine, 5-fluorouracil, methotrexate and hydroxyurea. Tape stripping, done 14 h before UV irradiation, stimulated SBC production as well as DNA synthesis (labeling index), while increased SBC counts, together with the high labeling index, showed a parallel decrease when the chemicals were given immediately after tape stripping. These results suggest that the cells proliferating at a higher rate than in other cells may be sensitive to UV and converted to SBC.