The relaxant effect of xenin on rat ileum is mediated by apamin
-sensitive neurotensin type receptors.
Clemens, Andreas, Stavros Katsoulis, Rainer Nustede, J[diaeresis]org
Seebeck, Klaus Seyfarth, Corinna Morys-Wortmann, Gerhard E. Feurle,
Ulrich R. F[diaeresis]olsch, and Wolfgang E. Schmidt.
Laboratory of Molecular Gastroenterology, Gastrointestinal Unit, I.
Department of Medicine, University of Kiel; Department of Surgery,
University of G[diaeresis]ottingen, D-37075 G[diaeresis]ottingen;
Department of Immunochemistry, Max-Planck-Institute for Experimental
Medicine, D- 37075 G[diaeresis]ottingen; and DRK-Hospital Neuwied, D-
56564 Neuwied, Germany
APStracts 3:0196G, 1996.
The action of xenin, a novel 25-residue peptide of the neurotensin
(NT)/xenopsin family, was investigated in isolated rat ileal muscle
strips and in dispersed longitudinal smooth muscle cells of rat small
intestine in vitro. Xenin relaxes KCl-precontracted ileal strips
dose-dependently [1 nM - 1 [mu]M]. The order of potency of the
investigated peptides was: xenopsin = NT = xenin > neuromedin
N. Kinetensin was inactive. Tetrodotoxin (TTX), hexamethonium,
tetraethylammonium, 4-aminopyridine and NG-nitro-L-arginine (L-NNA)
did not influence the relaxant effects of xenin or NT whereas the
potassium channel blocker apamin nearly abolished their effects.
Desensitisation against one of the peptides or blockade of NT
-receptors by SR48692 prevented the effect of xenin and NT. Structure
-activity-experiments revealed that the C-terminal part of the
molecules of xenin and NT are essential for biological activity.
Experiments with isolated dispersed smooth muscle cells and binding
studies on intestinal smooth muscle cell membranes confirmed and
extended the results obtained with muscle strips. In conclusion,
xenin relaxes rat ileal smooth muscle via a muscular NT type, apamin
-sensitive receptor.
Received 2 January 1996; accepted in final form 29 August 1996.
APS Manuscript Number G2-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996