Muscle metaboreflex control of coronary blood flow
1 Department of Physiology, 2 Department of Medicine, John D. Dingell Veterans Administration Medical Center, and 3 Department of Surgery, Wayne State University School of Medicine, Detroit, Michigan 48201 We investigated the effect of muscle metaboreflex activation on left circumflex coronary bl...
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Published in | American journal of physiology. Heart and circulatory physiology Vol. 283; no. 2; pp. H526 - H532 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
01.08.2002
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Subjects | |
Online Access | Get full text |
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Summary: | 1 Department of Physiology,
2 Department of Medicine, John D. Dingell Veterans
Administration Medical Center, and 3 Department of
Surgery, Wayne State University School of Medicine, Detroit,
Michigan 48201
We
investigated the effect of muscle metaboreflex activation on left
circumflex coronary blood flow (CBF) and vascular conductance (CVC) in
conscious, chronically instrumented dogs during treadmill exercise
ranging from mild to severe workloads. Metaboreflex responses were also
observed during mild exercise with constant heart rate (HR) of 225 beats/min and 1 -adrenergic receptor blockade to
attenuate the substantial reflex increases in cardiac work. The muscle
metaboreflex was activated via graded partial occlusion of hindlimb
blood flow. During mild exercise, with muscle metaboreflex activation,
hindlimb ischemia elicited significant reflex increases in mean
arterial pressure (MAP), HR, and cardiac output (CO) (+39.0 ± 5.2 mmHg, +29.9 ± 7.7 beats/min, and +2.0 ± 0.4 l/min,
respectively; all changes, P < 0.05). CBF increased
from 51.9 ± 4.3 to 88.5 ± 6.6 ml/min, ( P < 0.05), whereas no significant change in CVC occurred (0.56 ± 0.06 vs. 0.59 ± 0.05 ml · min 1 · mmHg 1 ;
P > 0.05). Similar responses were observed during
moderate exercise. In contrast, with metaboreflex activation during
severe exercise, no further increases in CO or HR occurred, the
increases in MAP and CBF were attenuated, and a significant reduction
in CVC was observed (1.00 ± 0.12 vs. 0.90 ± 0.13 ml · min 1 · mmHg 1 ;
P < 0.05). Similarly, when the metaboreflex was
activated during mild exercise with the rise in cardiac work lessened
(via constant HR and 1 -blockade), no increase in CO
occurred, the MAP and CBF responses were attenuated (+15.6 ± 4.5 mmHg, +8.3 ± 2 ml/min), and CVC significantly decreased from
0.63 ± 0.11 to 0.53 ± 0.10 ml · min 1 · mmHg 1 . We
conclude that the muscle metaboreflex induced increases in sympathetic
nerve activity to the heart functionally vasoconstricts the coronary vasculature.
exercise; ischemia; skeletal muscle; vascular
conductance |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0363-6135 1522-1539 |
DOI: | 10.1152/ajpheart.00152.2002 |