Intrahepatic bile ducts transport water in response to absorbed glucose

The physiological relevance of theabsorption of glucose from bile by cholangiocytes remains unclear. Theaim of this study was to test the hypothesis that absorbed glucosedrives aquaporin (AQP)-mediated water transport by biliary epitheliaand is thus involved in ductal bile formation. Glucose absorption andwater transport by biliary epithelia were studied in vitro bymicroperfusing intrahepatic bile duct units (IBDUs) isolated from ratliver. In a separate set of in vivo experiments, bile flow andabsorption of biliary glucose were measured after intraportal infusionof D-glucose or phlorizin. IBDUs absorbedD-glucose in a dose- and phlorizin-dependent manner with anabsorption maximum of 92.8 ± 6.2 pmol · min¹ · mm¹.Absorption of D-glucose by microperfused IBDUs resulted inan increase of water absorption (J_v = 310nl · min¹ · mm¹,P_f = 40 × 10³ cm/sec).Glucose-driven water absorption by IBDUs was inhibited byHgCl₂, suggesting that water passively followsabsorbed D-glucose mainly transcellularly viamercury-sensitive AQPs. In vivo studies showed that as the amount ofabsorbed biliary glucose increased after intraportal infusion ofD-glucose, bile flow decreased. In contrast, as theabsorption of biliary glucose decreased after phlorizin, bile flowincreased. Results support the hypothesis that the physiologicalsignificance of the absorption of biliary glucose by cholangiocytes islikely related to regulation of ductal bile formation.