Norepinephrine and serotonin vasoconstriction in rat hindlimb
control different vascular flow routes.
Newman, John Mb, Kim A Dora, Stephen Rattigan, Stephen J Edwards, Eric
Q Colquhoun, and Michael G Clark.
Department of Biochemistry, University of Tasmania, GPO Box 252C
HOBART 7001 Australia
APStracts 2:0227E, 1995.
The vasoconstrictors, norepinephrine at low dose (=0.1 [mu]M; LDNE)
and serotonin (5-HT) produce opposing metabolic effects in the
constant flow perfused rat hindlimb characterized by increased, and
decreased oxygen uptake (O2), respectively. In the present study the
effects of each vasoconstrictor are compared in the red blood cell
-free buffer perfused hindlimb on post-equilibration endogenous red
blood cell efflux, vascular entrapment of fluorescein-labelled
dextran (Fx) and vascular corrosion casting using 30 [mu]m methyl
methacrylate (MM). A marked transient washout of red blood cells
occurred immediately in association with vasoconstriction induced by
LDNE that was not apparent when a similar extent of vasoconstriction
was induced by 5-HT. Fx perfusions indicated that LDNE recruited a
new vascular space that was re-accessed by a second exposure to the
vasoconstrictor. 5-HT closed off a previously perfused vascular space
that was re-accessed when the vasoconstrictor was removed. Corrosion
casting of the arterial tree with MM showed no increase in cast
weight but more vessels filled due to LDNE. Higher doses of NE (2.5
[mu]M) or 5-HT, caused a marked decrease in cast weight with fewer
vessels filled. The data suggest that LDNE and 5-HT, in association
with vasoconstriction at different sites, control different capillary
flow routes in the hindlimb that in turn may influence metabolism by
increasing or decreasing nutrient access, respectively.
Received 12 June 1995; accepted in final form 7 November 1995.
APS Manuscript Number E269-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95