Ferguson, Scott K, Hirai, Daniel M, Copp, Steven W, Holdsworth, Clark T, Allen, Jason, Jones, Andrew M, Musch, Timothy I and Poole, David C (2013) Effects of nitrate supplementation via beetroot juice on contracting rat skeletal muscle microvascular oxygen pressure dynamics. Respiratory Physiology and Neurobiology, 187 (3). pp. 250-255. ISSN 1569-9048 (print) 1878-1519 (online)

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.

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