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Effect of dietary nitrate on sympathetic vasoconstriction in resting and contracting skeletal muscle

  • Author / Creator
    de Vries, Christopher James
  • Dietary nitrate (NO3-) may increase nitric oxide (NO) bioavailability and alter the control of blood flow at rest and during exercise. This thesis investigated the effect of dietary NO3- supplementation on sympathetic mediated control of skeletal muscle blood flow in resting and contracting skeletal muscle. It was hypothesized that dietary NO3-: 1) would not alter plasma norepinephrine (NE) at rest, during exercise and in response to a sympatho-excitatory stimulus; 2) would attenuate blood pressure and sympathetic vasoconstrictor responsiveness at rest and during exercise and enhance functional sympatholysis. In a double-blind randomized crossover design 10 men (22±2.8 yrs.) performed a cold pressor test (CPT) at rest and during moderate- (30% WRmax) and heavy-intensity (60% WRmax) alternate-leg knee-extension exercise following consumption of either NO3--rich beetroot juice (~12.9 mMol NO3-) or a NO3--depleted placebo (~0.13 mMol NO3-). Venous blood was sampled before and after the consumption of beetroot juice and at rest and during exercise and each CPT. Heart rate and BP were measured continuously via ECG and Finometer, and mean blood velocity (MBV) was measured continuously via Doppler ultrasound. Leg Blood flow (LBF; ml·min−1) was calculated as MBV (cm·s−1)·π·vessel radius2·60. Femoral vascular conductance (FVC; L·min-1·mmHg-1) was calculated as LBF/MAP. Sympathetic vasoconstrictor responsiveness to a CPT was calculated by determining the magnitude of the decrease in FVC during the CPT at rest and during exercise. The magnitude of functional sympatholysis was calculated as FVC at rest (% change) – FVC during exercise (% change). Plasma [NO3-] was significantly elevated following consumption of NO3- rich beetroot juice, but not NO3--depleted placebo (NO3-: 9±4 a.u. ;Placebo: 2±1 a.u.). Dietary NO3- did not alter sympathetic vasoconstrictor responsiveness at rest (NO3-: -33±10 %; Placebo: -34±11 %), or during moderate- (NO3-: -17±10 %; Placebo: -21±10 %) or heavy-intensity (NO3-: -12±9 %; Placebo: -11±10 %) exercise. Sympatholysis was also not altered during moderate- (NO3-: -16±11 %; Placebo: -13±8 %) or heavy-intensity (NO3-: -21±11 %; Placebo: -23±6 %) exercise following NO3- supplementation. These data demonstrate that acute dietary NO3- supplementation did not alter the regulation of blood pressure at rest and in response to exercise and sympatho-excitation. In conclusion, acute dietary NO3- supplementation did not alter sympathetic nervous system mediated vascular control at rest or during exercise in healthy young men.

  • Subjects / Keywords
  • Graduation date
    2015-11
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3154F126
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Physical Education and Recreation
  • Supervisor / co-supervisor and their department(s)
    • Dr. Darren DeLorey (Faculty of Physical Education and Recreation)
  • Examining committee members and their departments
    • Dr. Craig Steinback (Faculty of Physical Education and Recreation)
    • Dr. Margie Davenport (Faculty of Physical Education and Recreation)