has been identified as secretagogue. The observed increase The aim was to explore whether biliary epithelial cells in bile flow is of ductular origin. 4,5 Recent findings in biliary show muscarinic acetylcholine receptors and to investiepithelial cells have elucidated the mechanism of secretin gate their role in ductular bile formation. In both, isoinduced choleresis. investigated in a model with a high proportion of ductular bile flow, namely the isolated perfused guinea pig. Biliary epithelial cells line the intra-and extrahepatic biliary tree. They begin with small cuboidal cells at the canal of
MATERIALS AND METHODS
Hering and form ultimately the extrahepatic common bile
Materials.Male Wistar rats (250-300 g) and guinea pigs were duct.1,2 Although biliary epithelial cells account for only 3% obtained from the animal facilities of the University of Heidelberg, to 5% of the overall population of liver cells, this epithelium and housed in temperature and humidity controlled animal quarters provides a large surface area for electrolyte and fluid ex-on a 12-hour light/dark cycle. They were allowed free access to the standard chow and tap water until the time of the study. The animal change.3 Several hormones are involved in intestinal fluid experiments had been reviewed and permitted by a state board on secretion and absorption. In biliary epithelial cells secretin animal experimentation. Collagenase type I, carbamylcholine chloride (carbachol), and 2,5-di-tert-butylhydroquinone (tBuBHQ) were obtained from Sigma (Munich, FRG). DNAse type I, pronase, and trypsin were from Boeh- (1,1-dioctadedyl-3,3,3-tetra methylindocarbocyanine perchlorate) Received August 2, 1996; accepted December 20, 1996. (Dil-Ac-LDL) were from Molecular Probes Inc. (Eugene, OR). All first perfused for 15 minutes with a gazed buffer of 0.2 mmol/L eg-