Renal vasoconstrictor responses to static exercise during orthostatic stress in humans: Effects of the muscle mechano- and the baroreflexes

Afsana Momen, Karen Thomas, Cheryl Blaha, Amir Gahremanpour, Ather Mansoor, Urs A. Leuenberger, Lawrence I. Sinoway

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Renal circulatory adjustments to stress contribute to blood pressure and volume regulation. Both handgrip (HG) and disengagement of baroreflexes with lower body negative pressure (LBNP) can engage the sympathetic nervous system (SNS). However, the effect of simultaneous HG and LBNP on the renal circulation in humans is not known. Eighteen young healthy volunteers were studied. Beat-to-beat changes in renal blood flow velocity (RBV; Duplex Ultrasound), mean arterial pressure (MAP; Finapres) and heart rate (ECG) were monitored during (a) 15 s HG at 30% maximum voluntary contraction (MVC); (b) LBNP at -10 and -30 mmHg (each level for 5 min); and (c) 15 s HG (at 30% MVC) during LBNP at both levels. Renal vascular resistance index (RVR units) was calculated by dividing MAP by RBV. The increases in RVR during HG alone (12 ± 6%) were not different from the responses noted during combined HG and LBNP (17 ± 6% at -10 mmHg and 25 ± 8% at -30 mmHg). These results suggest occlusion occurs between a neural circuit engaged during 15 s of HG (central command and/or the muscle mechanoreflex) and a circuit activated by LBNP. In additional experiments (n = 6), similar non-algebraic summation of RVR was seen during 15 s involuntary biceps contractions (engages only muscle reflexes) and LBNP. With respect to RVR, neural occlusion occurs between baroreflexes and the muscle mechanoreflex. Muscle mechanoreflex mediated renal vasoconstriction during short bouts of HG is not influenced by baroreflex disengagement.

Original languageEnglish (US)
Pages (from-to)819-825
Number of pages7
JournalJournal of Physiology
Volume573
Issue number3
DOIs
StatePublished - Jun 15 2006

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Lower Body Negative Pressure
Baroreflex
Vasoconstrictor Agents
Exercise
Kidney
Muscles
Renal Circulation
Social Adjustment
Blood Flow Velocity
Sympathetic Nervous System
Vasoconstriction
Blood Volume
Vascular Resistance
Reflex
Healthy Volunteers
Arterial Pressure
Electrocardiography
Heart Rate
Blood Pressure

All Science Journal Classification (ASJC) codes

  • Physiology

Cite this

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title = "Renal vasoconstrictor responses to static exercise during orthostatic stress in humans: Effects of the muscle mechano- and the baroreflexes",
abstract = "Renal circulatory adjustments to stress contribute to blood pressure and volume regulation. Both handgrip (HG) and disengagement of baroreflexes with lower body negative pressure (LBNP) can engage the sympathetic nervous system (SNS). However, the effect of simultaneous HG and LBNP on the renal circulation in humans is not known. Eighteen young healthy volunteers were studied. Beat-to-beat changes in renal blood flow velocity (RBV; Duplex Ultrasound), mean arterial pressure (MAP; Finapres) and heart rate (ECG) were monitored during (a) 15 s HG at 30{\%} maximum voluntary contraction (MVC); (b) LBNP at -10 and -30 mmHg (each level for 5 min); and (c) 15 s HG (at 30{\%} MVC) during LBNP at both levels. Renal vascular resistance index (RVR units) was calculated by dividing MAP by RBV. The increases in RVR during HG alone (12 ± 6{\%}) were not different from the responses noted during combined HG and LBNP (17 ± 6{\%} at -10 mmHg and 25 ± 8{\%} at -30 mmHg). These results suggest occlusion occurs between a neural circuit engaged during 15 s of HG (central command and/or the muscle mechanoreflex) and a circuit activated by LBNP. In additional experiments (n = 6), similar non-algebraic summation of RVR was seen during 15 s involuntary biceps contractions (engages only muscle reflexes) and LBNP. With respect to RVR, neural occlusion occurs between baroreflexes and the muscle mechanoreflex. Muscle mechanoreflex mediated renal vasoconstriction during short bouts of HG is not influenced by baroreflex disengagement.",
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Renal vasoconstrictor responses to static exercise during orthostatic stress in humans : Effects of the muscle mechano- and the baroreflexes. / Momen, Afsana; Thomas, Karen; Blaha, Cheryl; Gahremanpour, Amir; Mansoor, Ather; Leuenberger, Urs A.; Sinoway, Lawrence I.

In: Journal of Physiology, Vol. 573, No. 3, 15.06.2006, p. 819-825.

Research output: Contribution to journalArticle

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T2 - Effects of the muscle mechano- and the baroreflexes

AU - Momen, Afsana

AU - Thomas, Karen

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AU - Gahremanpour, Amir

AU - Mansoor, Ather

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AU - Sinoway, Lawrence I.

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