PEPTIDE YY, GLUCAGON-LIKE PEPTIDE-1, AND NEUROTENSIN RESPONSES TO LUMINAL FACTORS IN THE ISOLATED VASCULARLY PERFUSED RAT ILEUM

Exposure of the ileum to nutrients markedly inhibits several upper gas trointestinal functions. Hormonal peptides of the ileal wall, i.e. pep tide YY (PYY), glucagon-like peptide-1 (GLP-1), and neurotensin (NT), are thought to play a role in this negative feedback mechanism. The pr esent study was conducted to comparatively assess the secretion of PW, GLP-1, and NT upon luminal infusion of a variety of individual lumina l factors in the isolated vascularly perfused rat ileum preparation. P W, GLP-1, and NT were measured in the portal effluent with specific RI As. Glucose (250 mM) induced a pronounced release of the three peptide s, whereas a physiological concentration of 5 mM did not induce peptid e secretion. Peptone (5%, wt/vol) evoked a sustained release of PW, GL P-1, and NT. Only NT secretion was increased upon luminal administrati on of 100 mM sodium oleate. Short chain fatty acids (20 mM)) evoked an early and transient release of the three peptides. In contrast, tauro cholate (20 mw) induced a sustained release of PYY, GLP-1, and NT, but the threshold concentration for peptide release was lower for NT than for PYY or GLP-1. Cellulose or pectin (0.5%, wt/vol) did not modify p eptide secretion. In conclusion, glucose and peptone are potent stimul ants of PYY, GLP-1, and NT release. Only NT is released upon oleic aci d stimulation. Finally, taurocholate is a potent stimulant of the rele ase of the three peptides. Overall, PW, GLP-1, and NT may participate cooperatively in the ileal brake. As relatively high concentrations of the various stimulants were required to elicit peptide release, it se ems likely that this mechanism operates in cases of maldigestion or ma labsorption.