Abstract: Objective To compare the effects of UVA irradiation on cell morphology,quantity and expression of inducible nitric oxide synthase (iNOS) mRNA and protein in human fibroblasts versus a keratinocyte cell line HaCaT.Methods Human fibroblasts and HaCaT cells were cultured and irradiated by 5 J/cm² UVA.Then,at 24,48 and 72 h after the stimulation,the cell morphology was observed under an inverted microscope,and iNOS mRNA and protein were measured by RT-PCR and immunohistochemistry method,respectively.Results After the irradiation,human fibroblasts showed shrinkage at the three time points,the quantities of the cells began to decrease significantly at 24 h (P<0.05),and iNOS mRNA and protein expression peaked at 24 h.However,HaCaT cells seemed not to shrink at any of the three time points.Moreover,the quantity of HaCaT cells was observed to decrease significantly at 48 h after the irradiation,and iNOS mRNA and protein expression also peaked at this time point.Conclusions As compared with HaCaT cells,human fibroblasts are more vulnerable to UVA,and their iNOS expression peaks earlier and lasts longer after UVA irradiation.

Key words: Ultraviolet rays, Fibroblasts, Nitric oxide synthase, HaCaT cells