Objective    To clarify the changes and significance of C-ski and Smad3 in rat skin fibroblast exposed to radiation.     Methods    The radiation induced injury of rat skin fibroblast was made by exposure to Soft X ray. Protein and mRNA expressions of C-ski and Smad3 were detected by Western blot and RT-PCR. The transcriptional activity of Smad3 was observed by electrophoretic mobility shift assay (EMSA).     Results    At 2 h after radiation

there were no obvious changes in protein and mRNA expression levels of C-ski

Smad3 or the transcriptional activity of Smad3. At 4 h

the expression of C-ski began to gradually decrease

reaching the minimum at 8 h

and Smad3 and Smad3 transcriptional activity began to increase

peaking at 8 h.      Conclusion    C-ski and Smad3 are involved in the pathological process of radiation induced fibroblast injury. Radiation can decrease C-ski and increase Smad3 expression

resulting in elevated Smad3 transcription activity

therefore cell proliferation is repressed and cell apoptosis is increased.