AIM To investigate the role of sphincter of Boyden in bile excretion and its regulating factors.METHODS Perfusion manometry, choledocho-cineradiography, reaction of the sphincter of Boyden toendogenous cholecystokinin (CCK) and immunohistochemical quantitative analysis were performed in 16dogs to study the motility and morphology of the sphincter of Boyden in experimental (postcholecystectomy)group ( n = 8) and the control group (n = 8).RESULTS The bile duct surrounded by SB was a low-pressure lumen (10.0 ± 2.0 mmHg), in which thepressure was significantly different (P<0.01, t = 6. 195) from the basal pressure of the high-pressure area ofsphincter of Oddi (SO), its basal pressure (SOBP) was 16.9±0.5 mmHg. The SB was an enlarged ampulladuring bile excretion interval, and showed active contraction during bile excretion. Intrinsic CCK could causediastole of SO, but does not affect the systole and diastole of SB. After cholecystectomy, spastic contractionpersisted in SB, which could not be relieved by intrinsic CCK. The sensitivity to CCK of SO was decreased,and the evacuation time of media prolonged (27.0±3.4 min vs precholecystectomy 17.l±0.9min P<0.01,t =7.961). In immunohistochemistry analysis, the contents of a-actin, myosin in the SB of experimentalgroup showed no increase. Under electronic microscope, the main changes were 3D structuraldisarrangement of the cell framework, distortion of the microfilaments, swelling and aggregation ofmitochondria at the nuclear side.CONCLUSION The excretion of bile can be divided into two types, physiological bile excretion with a drivemainly caused by the contraction of SB, and the other, functional bile excretion with a drive mainly causedby the contraction of gallbladder. It seems that the function of SB was controlled by vagus, whereas SO wasmore sensitive to the intrinsic CCK, The intact gallbladder is an elemental factor of functional coordinationof SB and SO.