Augmented mesenteric and renal vasoconstriction during exercise in
senescent fischer 344 rats.
Kregel, Kevin C.
Department of Exercise Science, The University of Iowa, Iowa City,
Iowa 52242
APStracts 2:0183A, 1995.
The purpose of this study was to test the hypothesis that
vasoconstriction in the mesenteric and renal circulations is greater
at both submaximal and maximal exercise intensities with advancing
age. Arterial blood pressure, heart rate, and mesenteric, renal, and
iliac (hindlimb) artery blood flow velocities (Doppler flow probes)
were measured before and during graded treadmill exercise in mature
(12 mo) and senescent (24 mo) male Fischer 344 rats. Maximal oxygen
consumption was reduced by 16% in the senescent rats (P < 0.05).
There were no differences in the two age groups during resting
conditions. During treadmill running at mild, moderate, and maximal
exercise intensities ( nearly equal to 45, 70, and 100% of maximal
oxygen uptake), the increases in arterial pressure were similar in
the mature and senescent animals, while heart rate rose less in the
older group (P < 0.05). Mesenteric and renal flow velocities
declined and vascular resistances increased from resting levels in
both groups in response to graded exercise; however, the magnitudes
of the increases in both mesenteric and renal vascular resistance
were significantly augmented in the older rats at the moderate and
maximal workloads. Hindlimb blood flow velocity increased and
resistance declined from resting levels at each exercise intensity in
both groups. In contrast to the visceral and renal adjustments, the
magnitudes of the changes in both hindlimb flow and resistance were
similar for the two age groups at all exercise intensities. Plasma
norepinephrine and epinephrine levels were not different between the
mature and senescent groups during resting conditions. Within each
group, the absolute concentrations of norepinephrine and epinephrine
were markedly elevated at the end of exercise compared with resting
values (P < 0.05). However, the magnitude of the rise in
norepinephrine was significantly greater in the senescent animals,
while the increase in epinephrine was similar in the two age groups.
These findings support the hypothesis that mesenteric and renal
vasoconstriction is augmented in senescent Fischer 344 rats during
exercise at moderate and maximal intensities, but not at mild
workloads. Despite these regional differences, the maintenance of
arterial pressure is not altered at either submaximal or maximal
exercise intensities with advancing age.
Received 25 July 1994; accepted in final form 24 April 1995.
APS Manuscript Number A755-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.