Effects of ischemia-reperfusion on vascular contractility and a1-adrenergic receptor
signaling in the rat tail artery.
Seasholtz, Tammy M., Guoping Cai, Hoau-Yan Wang, and Eitan Friedman.
Department of Pharmacology and Physiology, MCP Hahnemann School of Medicine,
Philadelphia, Pennsylvania 19102
APStracts 8:0257A, 2001.
To determine the effects of ischemia-reperfusion (I/R) on a1-adrenergic-receptor (a1-
AR) functions, a1-AR-mediated contraction, inositol phosphate (IP) accumulation, and
a1-AR-G protein coupling were examined in the tail arteries of anesthetized rats after 60
min of ischemia and 60 min of reperfusion. The contractile response to norepinephrine
(NE) was significantly increased after I/R, whereas the contractile response to KCl
remained unchanged. This was accompanied by a 69% increase in NE-stimulated IP
accumulation. Furthermore, receptor-stimulated coupling of a1a-AR to Gaq/11 proteins
was increased, whereas the coupling of a1b-AR or a1d-AR to their G proteins was not
altered by I/R. These changes in vascular a1-AR function occurred without concurrent
alteration in expression levels of membrane a1-AR subtypes or in the associated G
proteins. These data demonstrate that I/R increases a1a-AR-Gq/11 protein coupling and
a1-AR-stimulated IP accumulation in the tail artery. The alterations in a1-AR signaling
are associated with and may underlie the enhanced contractile response of the tail artery
to adrenergic stimulation after I/R.
Received 27 March 2001; accepted in final form 8 May 2001
APS Manuscript Number A295-1.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 18 June 2001