Intracellular pH regulation in bombesin-stimulated secretion in isolated bile duct units from rat liver

Abstract

Bombesin, a neuropeptide, stimulates fluid and [Formula: see text] secretion from cholangiocytes, but the underlying mechanisms are poorly understood. In this study, we aimed to examine the effects of bombesin on ion transport processes involved in the regulation of intracellular pH (pHi) and[Formula: see text] secretion in polarized cholangiocytes. Isolated bile duct units from normal rat liver were used to measure pHiby 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein 495 nm-to-440 nm dual ratio methods. Bombesin increased Cl−-[Formula: see text] exchange activity but did not affect basal pHior the activities of Na+/H+exchange or Na+-[Formula: see text] symport. Depolarization of cholangiocytes increased basal pHiand the activity of Cl−/[Formula: see text]exchange, suggesting that an electrogenic Na+-[Formula: see text]symport might function as a counterregulatory pHimechanism. Na+-independent acid-extruding mechanisms were not observed. We conclude that bombesin stimulates biliary secretion from cholangiocytes by activating luminal Cl−/[Formula: see text]exchange, which may be coupled to basolateral electrogenic Na+-[Formula: see text] symport.