Effects of exercise training on responses of peripheral and
visceral arteries in swine.
McAllister, Richard M., James K. Kimani, Jenny L. Webster, Janet L.
Parker, and M. Harold Laughlin.
Department of Veterinary Biomedical Sciences, College of Veterinary
Medicine, and Dalton Cardiovascular Research Center, University of
Missouri, Columbia, MO 65211
APStracts 2:0373A, 1995.
Studies have shown that the arterial vasculature serving skeletal
muscle ex hibits adaptations to exercise training that permit greater
blood flow in the trained state. We hypothesized that intrinsic
vasomotor reactivity of arteries to active mus cle during training
bouts would be altered to favor a relative vasodilation after train
ing. To test this hypothesis, miniature swine were either pen
-confined (SED; n=30) or treadmill-trained 5 d/wk over 16-20 wk (TRN;
n=32). A training bout in the final 4-8 wk of training consisted of
15 min of running at 6-8 mi/hr and 60 min of running at 4-5 mi/hr.
Efficacy of training was indicated by myocardial hypertrophy (SED,
4.84+/-0.11 g/kg bodyweight; TRN, 5.81+/-0.12; P<0.0005),
training bradycardia at several submax imal running speeds of a
maximal exercise test, increased running time to exhaustion during
that test (SED, 26+/-1 min; TRN, 35+/-1; P<0.0005), and
increased oxidative cap acities of several locomotory skeletal
muscles. Segments of femoral, brachial, mesen teric, renal, and
hepatic arteries were isolated from SED and TRN swine. Vascular rings
were prepared from these arterial segments, and their isometric
contractile and relaxation properties determined in vitro.
Contractile responses to KCl and norepin ephrine (NE) were
determined, as were relaxation responses to sodium nitroprusside and
adenosine, agents acting directly on vascular smooth muscle, and the
endothe lium-dependent agents bradykinin and the calcium ionophore
A23187. Responses to vasocontractile and vasorelaxation agents were
not different between SED and TRN for vessels serving active muscles
(i.e., femoral, brachial). On the other hand, renal arterial rings
from TRN exhibited lesser contractile responses than those from SED
across a range of NE concentrations (P<0.05), and 25% less
maximal contractile re sponse to NE (SED, 32.7+/-2.6 g; TRN, 24.2+/
-2.1; P<0.01). Responses of other vessels serving viscera (i.e.,
mesenteric, hepatic) were unchanged with training. These data
indicate that vasomotor reactivity of porcine conduit-type arteries
generally does not change with exercise training. An important
exception is the renal artery, which ex hibits a lesser contractile
response to NE in trained swine. This may contribute to better
preservation of renal blood flow during acute exercise in trained
animals.
Received 28 November 1994; accepted in final form 17 August 1995.
APS Manuscript Number A1209-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.