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Abstract

Enzyme, electrolyte, and fluid secretion from the exocrine pancreas is stimulated by neurotransmitter and peptide hormones [34, 35]. Whereas one group of secretagogues, to which belong β-adrenergic agonists, secretin, and vasoactive intestinal polypeptide (VIP), stimulate secretion by increasing cellular cAMP [6, 22], another group, including acetylcholine, cholecystokinin-pancreozymin, bombesin, and cerulein, act via an increase in the cytosolic-free Ca²⁺ concentration [21, 34]. We can distinguish two different types of electrolyte and fluid secretion. An isotonic NaCl secretion is produced in acinar cells by those secretagogues, which also release enzymes and whose action is mediated by Ca²⁺. In duct cells secretion and VIP stimulate a fluid rich in NaHC0₃ via increase of cellular cAMP. For both secretin and VIP, receptors are also present on acinar cells [8, 35] and stimulation also causes an increase in cAMP [28]. This, however, results in enzyme release, and probably not in secretion of NaHC0₃ and fluid from this type of cell.