BACKGROUND:?With the objective of developing a locally-produced radioactive stent, the present study used in vivo animal experiments to explore apoptosis of proliferative smooth muscle cells resulting from facilitation of the expression of genes caused byγ-radiation in order to prevent bile duct restenosis. We therefore explored the effects and signiifcance ofγ-radiation on the activity of caspase-3, Fas and Bcl-2 genes in apoptosis of proliferative smooth muscle cells in the bile duct walls of dogs. METHODS:Twelve dogs were randomly divided into 2 groups (6 in each group). A postinjury bile duct stenosis model was established and radioactive 103Pd (103palladium) or ordinary bile duct stents were implanted into the bile ducts. HE staining, RT-PCR and immunohistochemistry were used to detect the proliferation and apoptosis of bile duct smooth muscle cells in proliferative endomembrane and the expression of related caspase-3, Bcl-2 and Fas genes. RESULTS:?The expression of caspase-3 and Fas genes in the bile duct tissues of dogs with radioactive stents was higher than that of dogs with ordinary stents. There was signiifcant apoptosis of proliferative smooth muscle cells in the bile ducts. The expression of the Bcl-2 gene in the bile duct tissues of dogs with radioactive stents waslower than that in those with ordinary stents. There was signiifcant apoptosis of proliferative smooth muscle cells in the dogs with low Bcl-2 gene expression. CONCLUSIONS:? Radiation increases the activity of caspase-3 and Fas genes and is associated with apoptosis. The radioactive 103Pd stent may facilitate apoptosis of proliferative smooth muscle cells in the bile ducts of dogs by activating these genes. The Bcl-2 gene expression level is correlated with the occurrence of apoptosis and the radiosusceptibility of cells.