ObjectiveTo study the effect of BCL2 γradiation on BCL2 gene in dogs, and its relationship and signifcane on apoptosis of proliferated smooth muscle cells of bile duct wall. MethodsThe 103Pd radioactivity stent(experiment group) or ordinary stent(control group) was positioned into the target segment of bile duct. The injured bile duct segments were dissected free from the dogs, and BCL2 gene in the control and rradiationinduced apoptotic smooth mucle cells of bile duct wall was analysed by using immunohistochemical technique. The number of apoptotic cells was counted, and size of lumen of bile duct in both groups was measured by a computerized imaging system.ResultsBCL2 gene expression was weaker in the 103Pd radioactive stent group than in the ordinary stent group. The group of dogs with low expression of BCL2 genes showed marked apoptosis of proliferated smooth mucle cells of bile duct and there was no overt stenosis of extrahepatic bile ducts. The group that showed high expression of BCL2 gene did not show marked apoptosisi of proliferated smooth muscle cells of bile duct, and there was marked stenosis of extrahepatic bile duct.ConclusionsThe expression level of BCL2 in experimental dogs is related to the develoment of cellular apoptosis and to radiation sensitivity of the cells. 103Pd radioactive stent can reduce the expression of BCL2 gene, promote apoptosis of proliferated smooth muscle cells of bile duct, and suppress stricture formation of extrahepatic bile duct.