抄録
DNA damages and changes in proliferating activity of keratinocytes in rat dorsal skin exposed to a high-dose ultraviolet B (UVB) irradiation were examined immunohistochemically. The number of cells that express cyclobutane pyrimidine dimer (CPD), which represents UVB-induced DNA damage, started to increase at 1 h after irradiation, peaked at 3 h and thereafter decreased rapidly. Bromodeoxyuridine (BrdU)-labeling index (LI) was lower than that in control group from 1 to 24 h after irradiation, and it returned to the control level at 36 h. Topoisomerase II α (TIIα)-LI was significantly lower than that in control group from 1 to 12 h and showed the lowest value at 9 h. Thereafter, it increased and showed higher values than that in control group at 24, 36 and 72 h. These results suggest that DNA damages in survival basal keratinocytes may be repaired during 12 to 24 h and cell growth of keratinocytes may be arrested at least at 24 h.
