Regulation of colonic ion transport by gastrin releasing peptide:
i. grp stimulates transepithelial k and na secretion.
Traynor, Tim R., and Scott M. O'grady.
Department of Physiology, University of Minnesota, Minneapolis,
Minnesota 55455; and Departments of Physiology and Animal Science,
University of Minnesota, St. Paul, Minnesota 55108
APStracts 2:0383C, 1995.
Regulation of electrolyte transport across porcine distal colon
epithelium by gastrin-releasing peptide (GRP) was examined using
mucosal sheets mounted in Ussing chambers. Serosal GRP produced a
biphasic response consisting of a transient increase in short-circuit
current (Isc) followed by a long-lasting decrease. Indomethacin and
tetrodotoxin inhibited the Isc increase without affecting the
secondary decrease. Addition of GRP to the mucosal solution produced
a decrease in Isc similar to that observed with serosal treatment but
no transient increase in Isc was observed. GRP and bombesin (EC50's
of 26 and 30 nM respectively) were more effective than neuromedin B
in decreasing the Isc and the GRP receptor antagonist [D-Phe6]Bn(6
-13)OMe produced a 6 fold dextral shift in the GRP concentration
-response relationship. The GRP-stimulated decrease was reduced in the
absence of Cl and by serosal bumetanide. Flux measurements showed
that GRP increased Rb and Na secretion while having no effect on
transepithelial Cl transport. Phosphoinositide turnover was increased
by GRP suggesting that the ion transport changes may be mediated by
[Ca2+]i. The results of this study demonstrate that GRP stimulates K
and Na secretion across the porcine distal colon epithelium and that
these processes are dependent in part, on a bumetanide-sensitive
transport pathway located in the basolateral membrane.
Received 10 May 1995; accepted in final form 15 September 1995.
APS Manuscript Number C250-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95