THE PHYSIOLOGICAL-ROLE OF HISTAMINE IN THE EXOCRINE PANCREAS

In addition to the autonomic nervous system and gut hormones, the mast cell mediator histamine has also been associated with exocrine pancre atic secretion. This review is concerned with the distribution and the physiological role of histamine in the control of pancreatic juice se cretion. Histamine is distributed widely around blood vessels and acin ar tissues in the pancreas and it is released in pancreatic juice duri ng secretagogue stimulation. Histamine has a marked secretagogue effec t in the exocrine pancreas of several animal species but in many cases the secretory effect is gender-related. The paracrine hormone exerts its secretory response via activation of H-1 and H-2 receptors on panc reatic acinar cells to mobilize potassium ions (K+) and cellular calci um (Ca2+) and through elevation of endogenous adenosine 3',5' cyclic m onophosphate (cyclic AMP) levels, respectively. A physiological role f or H, receptors has also been associated with exocrine pancreatic secr etion. H-3 receptors are located presynaptically on parasympathetic ne rve terminals to control the release of acetylcholine via restriction of Ca2+ access into nerve terminal through the N-type Ca2+ channel. Ta ken together, the results presented in this review strongly support hi stamine as a potential modulator of exocrine pancreatic function.