Abstract: Objective To study the effects of insulin to the apoptosis and mitogen-activated protein kinase( MAPK ) signal transfer pathway of rat colonic smooth muscle cells ( SMCs ). Methods Enzymatic method for the isolation and culture of SD rat colonic SMCs; α-actin for immunohistochemical identification; division of the rat colonic SMCs into normal group, insulin group, and insulin+PD98059 group; MTT method for the detection of SMCs proliferation; flow cytometric Annexin V-FITC/ PI for the detection of SMCs apoptosis; and western blot for the detection of p-ERK, ERK, p-P38MAPK, P38MAPK and p-JNK, JNK expressions. Results Compared to the normal group, cells proliferation of insulin group is much more significant, apoptosis rate is reduced, p-ERK expression is enhanced, the ratio of p-ERK/ERK is increased( 110.36 ± 9.5 vs 50.92 ± 6.01 ) ( P < 0.01 ); and no differences for p-P38MAPK, P38MAPK, p-JNK and JNK expressions; while for the PD98059 group, cells proliferation is decreased significantly, apoptosis rate is increased, p-ERK expression is weakened, and the ratio of p-ERK/ERK is decreased( 15.69 ± 2.11 vs 50.92 ± 6.01 ) ( P < 0.01). Conclusion Insulin can promote proliferation and inhibit apoptosis in colonic SMCs through activation of the ERK route of MAPK pathway, P38MAPK and JNK routes may not be involved in this process.

Key words: Key words insulin, smooth muscle cells , apoptosis, MAPK pathway