title: Effects of nitrate supplementation via beetroot juice on contracting rat skeletal muscle microvascular oxygen pressure dynamics.
abstract: NO3(-) supplementation via beetroot juice (BR) augments exercising skeletal muscle blood flow subsequent to its reduction to NO2(-) then NO. We tested the hypothesis that enhanced vascular control following BR would elevate the skeletal muscle O2 delivery/O2 utilization ratio (microvascular PO2, PmvO2) and raise the PmvO2 during the rest-contractions transition. Rats were administered BR (~0.8 mmol/kg/day, n=10) or water (control, n=10) for 5 days. PmvO2 was measured during 180 s of electrically induced (1 Hz) twitch spinotrapezius muscle contractions. There were no changes in resting or contracting steady-state PmvO2. However, BR slowed the PmvO2 fall following contractions onset such that time to reach 63% of the initial PmvO2 fall increased (MRT1; control: 16.8±1.9, BR: 24.4±2.7 s, p<0.05) and there was a slower relative rate of PmvO2 fall (Δ1PmvO2/τ1; control: 1.9±0.3, BR: 1.2±0.2 mmHg/s, p<0.05). Despite no significant changes in contracting steady state PmvO2, BR supplementation elevated the O2 driving pressure during the crucial rest-contractions transients thereby providing a potential mechanism by which BR supplementation may improve metabolic control.
authors.affiliation: Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506-5802, USA.
authors.forename: Scott K
authors.initials: SK
authors.lastname: Ferguson
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Hirai
authors.forename: Steven W
authors.initials: SW
authors.lastname: Copp
authors.forename: Clark T
authors.initials: CT
authors.lastname: Holdsworth
authors.forename: Jason D
authors.initials: JD
authors.lastname: Allen
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
authors.forename: Timothy I
authors.initials: TI
authors.lastname: Musch
authors.forename: David C
authors.initials: DC
authors.lastname: Poole
mesh_terms: D000818:Animals; D027461:Beta vulgaris / Q000737:chemistry*; D001628:Beverages; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D019587:Dietary Supplements; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008833:Microcirculation; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D009566:Nitrates / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009566:Nitrates; D010100:Oxygen