Isolation of a Sialogogic Peptide from Bovine Hypothalamic Tissue and Its Characterization as Substance P

Abstract

A sialogogic peptide has been isolated from bovine hypothalami by gel filtration, ion exchange chromatography, and high voltage paper electrophoresis. The purity of this peptide was established by showing that the molar ratios of the constituent amino acids remained constant after high voltage paper electrophoresis at pH 1.9, 3.5, and 6.5. Its molecular weight (estimated by gel filtration) and its amino acid composition show that the peptide is an undecapeptide composed of Lys1, Arg1, Glx2, Pro2, Gly1, Leu1, Met1, and Phe2. The NH2-terminal residue is arginine. Further biological testing showed that the sialogogic peptide isolated is indistinguishable from Substance P; i.e. it stimulates contraction of the guinea pig ileum and the rat duodenum and is a potent vasodepressor. These effects are not inhibited by prior treatment of the test preparation with atropine. This report is believed to present the first complete purification of Substance P.