Physiology of Duct Cell Secretion

The roles of calcium and ATP in the physiology and pathology of the exocrine pancreas

“…In contrast, and in the same experiments, the CCK-elicited fluid and enzyme secretion was acutely abolished when Ca 2+ was omitted from the perfusion fluid (254,327). It has indeed been clear for many years that the action of secretin, stimulating ductal HCO 3 secretion, is mediated by cAMP (41,349), rather than -as is the case for ACh and CCK in acinar cellsby Ca 2+ (40,190,262).…”

“…Since the pancreatic acinar cells secrete the enzyme-rich fluid that is essential for the physiological digestion of food in the intestine (247), it is not surprising that Ca 2+ signalling studies have mostly been confined to these cells. Because the secretion of the bicarbonate-rich fluid from the pancreatic duct cells is principally controlled by the hormone secretin that activates adenyl cyclase, this secretion process is mainly a cyclic AMP regulated event (41,349) and consequently Ca 2+ signalling studies in the duct cells were for a long time neglected. It is, however, now clear that Ca 2+ signals evoked by ACh and ATP can occur in duct cells and could be physiologically important for the regulation of ductal bicarbonate secretion (113).…”

“…As described in section III, such information is available for the acinar cells. We can therefore be reasonably sure about the importance of ACh as a physiologically relevant transmitter controlling acinar cells function, but do not have such evidence for the duct cells.It certainly cannot be excluded that Ca 2+ signalling in duct cells has physiological importance, but it would appear that the principal function of the duct cells, namely the secretion of a bicarbonate-rich fluid, is mainly controlled by secretin via the intracellular messenger cAMP and that Ca 2+ signals, unlike in the acinar cells, only play a relatively minor role(349). Ca 2+ ] i and inhibited secretion (181).…”

The role of Ca2+ signaling in the physiology and pathophysiology of the pancreatic ductal cells

“…The amount of daily secreted pancreatic fluid in humans is between 1 liter and 2,5 liter. The secretion depends on the body size and reduces with age 8 . The physiological function of alkaline secretion is in one hand to neutralise protons secreted by acinar cells, to flush digestive enzymes to the duodenum, and to neutralise the gastric acid entering the duodenum 9 .…”

“…The secreted Cl − by acinar cells is exchanged for HCO3 − by the ductal cells to produce an alkaline fluid, which is essential for normal digestion 4,8,10 . The accumulation of HCO3inside the ductal cell across basolateral membrane thought to be mediated by direct mechanism through Na + / HCO3 − cotransporters (pNBC1) or indirectly via the passive diffusion of carbon dioxide (CO2) across the cell membrane.…”