Dynamic and ultrastructural study of sphincter of Oddi in early-stage cholelithiasis in rabbits with hypercholesterolemia

AIM To study the relationship between preformation of gallstone and the kinetics and ultrastructure of sphincter of Oddi.METHODS Adult female rabbits were used and divided into 3 groups, and fed with either normal or high cholesterol diet for four or eight weeks.Each group contained eight rabbits. The manometry of sphincter of Oddi, biliary cineradiography, gallbladder volume measurement and ultrastructure observation under electron microscope were performed.RESULTS In groups Ⅰ and Ⅱ, the basal pressure in low-pressure ampulla or high pressure zone of sphincter of Oddi was elevated, the amplitude of phasic contraction was decreased and the volume of gallbladder were increased, with a significant difference (P＜0.01) from those of control. Gallstones were found in group Ⅱ rabbits (7/8). Under cineradiography, low-pressure ampulla showed a spasmodic status without apparent peristaltic contraction. Under electron microscope, inside the muscular cells of sphincter of Oddi,loosening of microfilament and swelling of plasmosomes which congregated at the top were observed. The amount showed no obvious change under nitric oxide synthase (NOS) stain.CONCLUSION Twisting of the microfilament and disarrangement of kink macula densa inside the muscular cells suggested that the sphincter of Oddi was under spasmodic status. The impaired diastolic function caused and aggravated the stasis of cystic bile. The swelling plasmosome could be one of the important factors in elevating the tonic pressure of sphincter of Oddi.