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 bombesin-stimulated 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 video-microscopy 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.