Characterization of ion transport mechanisms involved in bombesin-stimulated biliary secretion in rat cholangiocytes

Background/Aims: Bombesin is a neuropeptide which stimulates fluid and bicarbonate secretion from cholangiocytes by stimulating Cl−/HCO3− exchange. However, the underlying regulation and interactions of ion transporters and channels mediating this bombesin-stimulated biliary secretion are not well characterized. The aim of the study was to characterize the ion transport processes involved in bombesinstimulated secretion in polarized cholangiocytes in comparison with those of secretin. Methods: Isolated bile duct units (IBDU) were prepared from normal rat liver. Biliary secretion induced by bombesin was measured by quantitative videomicroscopy in the presence and absence of inhibitors. Results: Bombesin-stimulated secretion was inhibited by H2-DIDS, NPPB, BaCl2, TEA, and acetazolamide. However, in contrast to secretin, bombesin-stimulated secretion was not inhibited by disruption of microtubules. Conclusions: Bombesin-stimulated biliary secretion is dependent on anion exchangers, Cl− and K+ channels, and carbonic anhydrase but not on microtubules. Bombesin regulates secretion in cholangiocytes by different mechanisms from those established for secretin.