The isolation of a new hypotensive peptide, neurotensin, from bovine hypothalami.

A hypotensive peptide, designated neurotensin, has been discovered and isolated in pure form from acid-acetone extracts of bovine hypothalami by column chromatography and paper electrophoresis. The results of amino acid analyses of material recovered after paper electrophoresis at pH 3.5, 6.5, and 8.9 and chromatographic analyses of the dansylated material indicate that the peptide isolated by this procedure is homogenous. Its amino acid composition and apparent molecular weight estimated by chromatography on Sephadex G-25 indicate that neurotensin is a tridecapeptide composed of Lys, Argz, Asx, Glxz, Proz, Ileu, Leuz, Tyr,. Neurotensin lacks a free NH2-terminus; however, it possesses a free COOH terminus which can be acted upon by carboxypeptidase A. Neurotensin induces hypotension in the rat and can stimulate the contraction of guinea pig ileum and rat uterus; however, it produces relaxation of the rat duodenum. These pharmacological properties classify it as a “kinin,” yet its chemical composition distinguishes it from any known peptide.