Regulatory Peptides, 20 (1988) 171-180 Elsevier 171 RPT 00665 [Arg3]substance P and neurokinin A from chicken small intestine J. Michael Conlon 1, Stavros Katsoulis 1, Wolfgang E. Schmidt z and Lars Thim 3 Clinical Research Groupfor Gastrointestinal Endocrinology of the Max-Planck-Gesellschaft and 2 Department of Medicine, University of G6ttingen, G6ttingen (F.R.G.) and 3Novo Research Institute, Bagsvaerd (Denmark) (Received 27 April 1987;revisedversionreceived 8 October 1987;accepted 8 October 1987) Summary Using antisera specific for NH2-terminal and COOH-terminal regions of sub- stance P and for the COOH-terminal region of neurokinin A, peptides with tachy- kinin-like immunoreactivity were isolated from extracts of chicken small intestine. The peptide Arg-Pro-Arg-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2 differs from human substance P by substitution of the lysyl residue by an arginyl residue at posi- tion 3. Synthetic [Arg3]substance P showed identical chromatographic and immu- nochemical properties to chicken substance P and was equipotent with substance P in contracting the guinea pig ileum. A second peptide His-Lys-Thr-Asp-Ser-Phe-Val- -Gly-Leu-Met-NH2 isolated from the extracts is identical to human neurokinin A. A third peptide was immunoreactive towards the COOH-terminally directed anti- serum to substance P only but was not characterized structurally in this study. Tachykinin; Chicken gut; Primary structure; HPLC; Radioimmunoassay Introduction The tachykinin family of polypeptides is widely distributed in nature but a sys- tematic approach to the structural characterization of the peptides has not been made. The nucleotide sequence of the cloned cDNAs for preprotachykinin has been Correspondence: J.M. Conlon,Klinische Arbeitsgruppeder MPG, GosslerstraBe10d,D-3400 G6ttingen, F.R,G. 0167-0115/88/$03.50 © 1988 ElsevierSciencePublishers B.V. (Biomedical Division)