Isolation of a tridecapeptide from bovine intestinal tissue and its partial characterization as neurotensin

Radioimmunoassayable neurotensin (R-NT) has been isolated from acid/acetone extracts of 50 kg of calf small intestine with an overall yield of approximately 15%. The concentration of R-NT in calf intestinal tissue was approximately 35 pmol/g wet weight. Throughout the purification procedures which involved adsorption onto sulfopropyl (SP)-Sephadex, chromatography on Sephadex G-25 and SP-Sephadex, immunoadsorption on neurotensin-antibody Sepharose and high voltage paper electrophoresis, R-NT displayed the chromatographic and electrophoretic properties of neurotensin. R-NT was found to contain a tridecapeptide with the same amino acid composition as neurotensin. This peptide yielded the same products as neurotensin when submitted to digestion by carboxypeptidase A or papain. Its immunological properties were indistinguishable from those of neurotensin and its potency in stimulating hypotension in anesthetized rats was comparable to that of synthetic neurotensin. If the amino acid sequence of this peptide proves to be the same as that of neurotensin, then neurotensin is another biologically active peptide isolated from both brain and intestinal tissues.