[Ser⁷]neurotensin: isolation from guinea pig intestine

Using three antisera to neurotensin of defined regional specificity, a novel neurotensin has been identified in extracts of guinea pig brain and small intestine. The primary structure of the peptide was established as: pGlu Leu Tyr GIu Asn Lys Ser Arg Arg Pro Tyr He Leu. Guinea pig neurotensin differs from bovine neurotensin by substitution of a prolyl residue by a seryl residue at position 7. Synthetic [Ser⁷]neurotensin showed identical Chromatographie and immunochemical properties to guinea pig neurotensin. This difference in primary structure may account for some of the anomalous pharmacological effects of bovine neurotensin on guinea pig tissues.