Abstract

Publisher Summary This chapter examines the peptidergic regulation of the cyclic AMP (cAMP) system in the intestinal epithelium. The cAMP system of the intestinal epithelium appears to be stimulated mainly through the vasoactive intestinal peptide (VIP) receptors. VIP is the most potent and/or efficient stimulant of cAMP production in intestinal epithelial cells (IEC). The other active substances are secretin and PHI, which are VIP agonists of low potency, prostaglandins E1, E2, and isoproterenol which are much less potent and efficient than VIP. The expression of VIP-binding sites and of a VIP-sensitive cAMP production system is not confined to the differentiated epithelial cells from the small intestinal villi. VIP receptors are also present in the undifferentiated epithelial crypt cells from the small intestine. VIP receptors appear to be expressed throughout the intestinal epithelium from duodenum to rectum. In that respect, the distribution of VIP receptors in IEC correlates well with the distribution of the VIP-containing nervous structures in the intestinal tract and strongly argues for the action of VIP through a local neuroparacrine pathway. The data summarized in the chapter supports a direct peptidergic control of cAMP metabolism and of cAMP-dependent transport processes in the intestinal epithelium.

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