Nitric oxide and the pancreas: Morphological base and role in the control of the exocrine pancreatic secretion

The distribution of nitric oxide synthase in both neuronal and non-neuronal pancreatic tissues and the role of nitric oxide in the control of exocrine pancreatic secretion are reviewed in this article. Earlier reports based o n in vivo studies suggested that nitric oxide can affect the secretory acti vity of the exocrine pancreas through changes in pancreatic blood flow. Mor e recently, the employment of either nitric oxide synthase inhibitors or ni tric oxide donors in in vitro preparations has provided evidence that nitri c oxide can exert a direct action on this gland independently on its vascul ar effects. Most research in this area seems to indicate that modulation of exocrine pancreatic function by nitric oxide is exerted via activation of guanylate cyclase and generation of cGMP, although other pathways cannot be excluded. Experiments performed over the last year in our laboratory revea l a novel and interesting mechanism based on the ability of nitric oxide to control the release of endogenous neurotransmitter in the pancreas and, su bsequently, the nerve-mediated enzyme secretion.