Expression of insulin-like growth factor-i receptors and binding
proteins by colonic smooth muscle cells.
Zeeh, J[diaeresis]org M., Helena S. Ennes, Peter Hoffmann, Frank
Procaccino, Viktor E. Eysselein, William J. Snape, Jr., and James A.
McRoberts.
Division of Gastroenterology, Department of Medicine, Harbor-UCLA
Medical Center, Torrance, CA 90502
APStracts 3:0185G, 1996.
We recently demonstrated up-regulation of Insulin-like growth factor-I
(IGF-I) binding sites in the smooth muscle layer of inflamed rat
colon. The increase in binding sites was due to increased expression
of IGF binding proteins (IGFBPs) which modulate the effects of IGF.
To further study the role of IGF in the colon, we investigated
whether cultured colonic smooth muscle cells (SMC) express IGF-I
receptors and IGFBPs. SMC were isolated by collagenase digestion from
rat colonic smooth muscle and grown in primary culture. Equilibrium
binding experiments using 125I-IGF-I showed the presence of an IGF-I
receptor with a KD of 1.96 nM and a Bmax of 53,000 receptors/cell.
Competition binding studies with IGF-II and insulin, together with
chemical crosslinking experiments corroborated this conclusion.
Western ligand blotting of conditioned media and Northern analysis of
total RNA demonstrated that the cells expressed and secreted IGFBP-4,
-5 and -3 with molecular weights of 25, 31 and 45 kDa, respectively.
These results together with our in vivo studies in the rat support a
role for IGF in tissue fibrosis and stricture formation during
chronic intestinal inflammation.
Received 27 November 1996; accepted in final form 11 September
1996.
APS Manuscript Number G503-6.
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