| Muscle chemoreflex-induced increases in right atrial pressure. | |
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MedLine Citation:
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PMID: 9724278 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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When oxygen delivery to active muscle is too low for the ongoing rate of metabolism, metabolites accumulate and stimulate sensory nerves within the muscle leading to sympathetic activation (muscle chemoreflex). To date, studies on this reflex have focused primarily on its ability to increase arterial pressure or on the activity of the nerves that mediate this response. Clearly, a rise in cardiac output (CO) constitutes an important adjustment, because it increases the total blood flow available to be distributed among organs competing for flow. However, increments in heart rate and contractility provide limited means of raising CO because of the inverse relationship that exists between CO and right atrial pressure (RAP) in the intact circulation. Our goal was to test whether muscle chemoreflex activation, achieved via graded reductions in hindlimb blood flow by partial vascular occlusion, elicits peripheral vascular adjustments that raise RAP. In four conscious dogs exercising on a treadmill at 3.2 km/h 0% grade, RAP was well maintained during reflex activation despite increases in CO and arterial pressure that are expected to reduce RAP. Thus peripheral vascular adjustments elicited by the reflex successfully defend RAP in a setting where it would otherwise fall. To isolate the effects of the reflex on RAP, CO was maintained constant by ventricular pacing in conjunction with beta1-adrenergic blockade with atenolol. When the reflex was activated by reducing hindlimb blood flow from 0.6 to 0.3 l/min, RAP rose from 5.1 +/- 0.8 to 7.4 +/- 0.4 mmHg (P < 0.05) despite continued large (40 mmHg) increases in arterial pressure. During heavier exercise (6.4 km/h 10% grade) in five dogs with normal ventricular function, the reflex raised RAP from 5.7 +/- 0.9 to 6.6 +/- 0.8 mmHg (P < 0.05) despite increases in CO and arterial pressure. We conclude that the muscle chemoreflex is capable of eliciting substantial increases in RAP. |
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Authors:
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D D Sheriff; R A Augustyniak; D S O'Leary |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: The American journal of physiology Volume: 275 ISSN: 0002-9513 ISO Abbreviation: Am. J. Physiol. Publication Date: 1998 Sep |
Date Detail:
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Created Date: 1998-10-01 Completed Date: 1998-10-01 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 0370511 Medline TA: Am J Physiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: H767-75 Citation Subset: IM; S |
Affiliation:
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Flight Motion Effects Branch, Air Force Research Laboratory, Brooks Air Force Base, San Antonio, Texas 78235. USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Atrial Function, Right / physiology* Blood Flow Velocity Blood Pressure / physiology* Cardiac Output Chemoreceptor Cells / physiology* Dogs Female Hindlimb / blood supply Male Muscle, Skeletal / innervation* Physical Exertion Reflex / physiology* Renal Circulation Sympathetic Nervous System / physiology* |
| Grant Support | |
ID/Acronym/Agency:
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HL-02844/HL/NHLBI NIH HHS; HL-46314/HL/NHLBI NIH HHS; HL-55473/HL/NHLBI NIH HHS |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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