The muscle content and contractile capability of the common bile duct.

The supraduodenal portion of the human and canine common bile duct has been shown by indirect immunofluorescent staining with anti-actin sera to contain scattered bundles of smooth muscle arranged predominantly in a longitudinal direction with respect to the axis of the bile duct. Isolated strips of canine common bile duct in vitro can contact in response to stimulation with cholecystokinin. The force of contraction in a longitudinal direction is about three times that in a transverse direction but only 3% of that produced by isolated gallbladder strips. There appears to be a roughly proportional relationship between the amount of muscle demonstrated and the force of contraction in response to cholecystokinin.