中文摘要：

目的：环丁烷嘧啶二聚体（CPDs）是细胞受紫外线损伤后产生的特征性光产物之一。本文观察UVB辐射后HaCaT细胞光产物CPDs的产生和清除没食子儿茶素没食子酸脂（epigallocatechingallate，EGCG）的干预作用。方法：以一定剂量UVB照射HaCaT细胞并用EGCG干预处理，采用免疫组织化学法在照光后不同时间点检测CPDs的产生和清除。结果：细胞损伤程度随UVB辐射剂量加大而增大。30mJ／cm^2 UVB辐射后HaCaT细胞开始产生CPDs，0．5h左右达到高峰。同时细胞也开始清除CPDs，辐射后4h内清除速率较快，4h后清除速率逐渐降低，至24h基本清除CPDs。EGCG处理UVB辐射的细胞CPDs少于单纯照光组（P〈0．05）。结论：细胞损伤程度随UVB辐射剂量增大而加重，UVB辐射后HaCaT细胞对CPDs的清除存在快速期和慢速期；EGCG可以降低UVB辐射所致的光产物水平。

英文摘要：

Objective Cyclobutane pyrimidine dimers （CPDs） are characteristic photoproducts in cells after ultraviolet irradiation. The study investigated the production and removal of photoproducts induced by UVB irradiation and intervention effect by epigallocatechingallate （EGCG） in human eternal keratinocyte line-HaCaT cells. Methods HaCaT cells were irradiated only by UVB or cultured with 200 ug/ml EGCG right after UVB irradiation. The production and removal of CPDs at different time intervals were examined by immunohistochemical method. Results The damage of HaCaT cells was increased in the dosage of UVB irradiation. CPDs appeared in HaCaT ceils and reached the peak at 0.5h and removed rapidly during the first 4h and then removed slowly or almost cleared out up to 24h after UVB irradiation. The quantity of CPDs was decreased when irradiated HaCaT cells were incubated with EGCG （P〈0.05）. Conclusions The photodamage of HaCaT cells was UVB dose dependent. There seems to be two phases in the removal of CPDs： a rapid phase and a slower phase after UVB irradiation. EGCG can de- crease the level of CPDs.