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Impact of dietary nitrate supplementation via beetroot juice on exercising muscle vascular control in rats
Author(s) -
Ferguson Scott K.,
Hirai Daniel M.,
Copp Steven W.,
Holdsworth Clark T.,
Allen Jason D.,
Jones Andrew M.,
Musch Timothy I.,
Poole David C.
Publication year - 2013
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2012.243121
Subject(s) - hindlimb , chemistry , skeletal muscle , blood pressure , blood flow , medicine , endocrinology , hemodynamics , nitric oxide , nitrite , dietary nitrate , treadmill , zoology , nitrate , biology , organic chemistry
Key points• Inorganic nitrate (NO 3 − ) supplementation with beetroot juice (BR) in humans lowers blood pressure and the O 2 cost of exercise and may improve exercise tolerance following its reduction to nitrite (NO 2 − ) and nitric oxide (NO). • The effect of inorganic NO 3 − supplementation with BR on skeletal muscle blood flow (BF) and vascular conductance (VC) within and among locomotory muscles during exercise is unknown. • Inorganic NO 3 − supplementation with BR in rats resulted in lower exercising mean arterial pressure, lower blood [lactate], and higher total skeletal muscle hindlimb BF and VC during submaximal treadmill running. • The greater BF and VC was found in muscles and muscle parts containing primarily type IIb + d/x muscle fibres. • These data demonstrate that inorganic NO 3 − supplementation improves vascular control and elevates skeletal muscle O 2 delivery during exercise predominantly in fast‐twitch type II muscles, and provide a potential mechanism by which NO 3 − supplementation improves metabolic control.Abstract Dietary nitrate (NO 3 − ) supplementation, via its reduction to nitrite (NO 2 − ) and subsequent conversion to nitric oxide (NO) and other reactive nitrogen intermediates, reduces blood pressure and the O 2 cost of submaximal exercise in humans. Despite these observations, the effects of dietary NO 3 − supplementation on skeletal muscle vascular control during locomotory exercise remain unknown. We tested the hypotheses that dietary NO 3 − supplementation via beetroot juice (BR) would reduce mean arterial pressure (MAP) and increase hindlimb muscle blood flow in the exercising rat. Male Sprague–Dawley rats (3–6 months) were administered either NO 3 − (via beetroot juice; 1 mmol kg −1 day −1 , BR n = 8) or untreated (control, n = 11) tap water for 5 days. MAP and hindlimb skeletal muscle blood flow and vascular conductance (radiolabelled microsphere infusions) were measured during submaximal treadmill running (20 m min −1 , 5% grade). BR resulted in significantly lower exercising MAP (control: 137 ± 3, BR: 127 ± 4 mmHg, P < 0.05) and blood [lactate] (control: 2.6 ± 0.3, BR: 1.9 ± 0.2 m m , P < 0.05) compared to control. Total exercising hindlimb skeletal muscle blood flow (control: 108 ± 8, BR: 150 ± 11 ml min −1 (100 g) −1 , P < 0.05) and vascular conductance (control: 0.78 ± 0.05, BR: 1.16 ± 0.10 ml min −1 (100 g) −1 mmHg −1 , P < 0.05) were greater in rats that received BR compared to control. The relative differences in blood flow and vascular conductance for the 28 individual hindlimb muscles and muscle parts correlated positively with their percentage type IIb + d/x muscle fibres (blood flow: r = 0.74, vascular conductance: r = 0.71, P < 0.01 for both). These data support the hypothesis that NO 3 − supplementation improves vascular control and elevates skeletal muscle O 2 delivery during exercise predominantly in fast‐twitch type II muscles, and provide a potential mechanism by which NO 3 − supplementation improves metabolic control.