Objective To estimate the effect and the intracellular signal transduction pathway of insulin-like growth factor I (IGF-I) on the expression of stem cell factor(SCF) in colonic smooth-muscle cells(SMC). Methods The SMCs isolated from colon of the SD rats by enzymolysis were cultured and identified by α-actin immunocytochemical method. Colonic SMCs were cultured either with 100 μg/L of IGF-I at different time points (0, 8, 16, 24 and 48 hours) or with different concentrations (0,5,10,50,100 and 150 μg/L) of IGF-I for 16 hours. The expressions of SCF in colonic SMCs pretreated with or without speicific phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor LY-294002 or mitogen-activated protein (MAP) kinase (MEK1) inhibitor PD-98059 were examined by Western blotting and quantitative reverse transeription-polymerase chain reaction and immunofluorescence. Results Low expression of SCF was found in colonic SMCs cultured in the bovine serum free medium. There was no effect of 5 or 10 μg/L of IGF- I on the expression of SCF. However, the expressions of SCF mRNA and protein were increased when stimulated with high concentrations (50,100,150 μg/L) of IGF-I. The peak expression of SCF was showed at the 16th hour after stimulating with 100 μg/L of IGF- I that was considered as the most effective concentration in vitro. The expression of SCF was not influenced by LY-294002, but was partly blocked by PD-98059. Conclusions The expression of SCF in colon SMCs may be induced by IGF-Ⅰ through MAP kinase signaling pathway.