AIM:To investigate the effect of gastrin on differentiationof IEC-6 cell line in vitro.METHODS:IEC-6 cells were incubated with gastrin.Onday 7 after treatment,cell morphology was examined bylight microscope,and on day 20,the cellular ultrastructureswere examined by electron microscope.After exposure togastrin for 6 hours,villin mRNA was analyzed by reversetranscription-polymerase chain reaction,and on day 7,theexpression of villin was examined by immunocytochemicalanalysis with laser confocal microscope.RESULTS:After exposure to gastrin,IEC-6 cells showeddifferentiated phenotypes as villas enterocytes and containedan abundance of plasma,small nuclei with nucleoli,andwere arranged regularly.There were numerous microvilliaround edge of the cells,and several cells showed columnarstructures.Villin mRNA expression in cytoplasm was increasedin comparison with control.CONCLUSION: Differentiated characteristics of villus enterocytes and phenotypic changes of rat intestinal epithelial cells (IEC-6) are induced by gastrin, and the effects of gastrin are correlated to increased villin expression. AIM: To investigate the effect of gastrin on differentiation of IEC-6 cell line in vitro. METHODS: IEC-6 cells were incubated with gastrin. Onday 7 after treatment, cell morphology was examined bylight microscope, and on day 20, the cellular ultrastructureswe examined by electron microscope. After exposure to gastrin for 6 hours, villin mRNA was analyzed by reversetranscription-polymerase chain reaction, and on day 7, theexpression of villin was examined by immunocytochemicalanalysis with laser confocal microscope .RESULTS: After exposure to gastrin, IEC-6 cells showed differentiated phenotypes as villas enterocytes and containedan abundance of plasma, small nuclei with nucleoli, andwere arranged regularly. There were numerous microvilliaround edges of the cells, and several cells showed columnarstructures. Villin mRNA expression in cytoplasm was increased in comparison with control. CONCLUSION: Differentiated characteristics of villus enterocytes and phenotypic changes of rat intestinal epithelial cells (IE C-6) are induced by gastrin, and the effects of gastrin are correlated to increased villin expression.