Dietary nitrate supplementation: impact on skeletal muscle vascular control in exercising rats with chronic heart failure

Chronic heart failure (CHF) results in central and peripheral derangements that ultimately reduce skeletal muscle O₂ delivery and impair exercise tolerance. Dietary nitrate (NO₃^–) supplementation improves skeletal muscle vascular function and tolerance to exercise. We tested the hypothesis that NO₃^– supplementation would elevate exercising skeletal muscle blood flow (BF) and vascular conductance (VC) in CHF rats. Myocardial infarction (MI) was induced (coronary artery ligation) in young adult male rats. After 21 days of recovery, rats randomly received 5 days of NO₃^–-rich beetroot juice (CHF + BR, n = 10) or a placebo (CHF, n = 10). Mean arterial pressure (carotid artery catheter) and skeletal muscle BF (radiolabeled microspheres) were measured during treadmill exercise (20 m/min, 5% grade). CHF-induced dysfunction, as determined by myocardial infarction size (29 ± 3% and 33 ± 4% in CHF and CHF + BR, respectively) and left ventricular end-diastolic pressure (18 ± 2 and 18 ± 2 mmHg in CHF and CHF + BR, respectively), and exercising mean arterial pressure (131 ± 3 and 128 ± 4 mmHg in CHF and CHF + BR, respectively) were not different (P > 0.05) between groups. Total exercising hindlimb skeletal muscle BF (95 ± 5 and 116 ± 9 ml·min^–1·100 g^–1 in CHF and CHF + BR, respectively) and VC (0.75 ± 0.05 and 0.90 ± 0.05 ml·min^–1·100 g^–1·mmHg^–1 in CHF and CHF + BR, respectively) were 22% and 20% greater in BR-supplemented rats, respectively (P < 0.05). During exercise, BF in 9 and VC in 10 hindlimb muscles and muscle portions were significantly greater in the CHF + BR group. These results provide strong evidence that dietary NO₃^– supplementation improves skeletal muscle vascular function during exercise in rats with CHF and, thus, support the use of BR as a novel therapeutic modality for the treatment of CHF.

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