Changes in body posture alter plasma nitrite but not nitrate concentration in humans

Liddle, L., Monaghan, C., Burleigh, M., McIlvenna, L., Muggeridge, D. and Easton, C. (2018) Changes in body posture alter plasma nitrite but not nitrate concentration in humans. Nitric Oxide, 72. pp. 59-65. ISSN 1089-8603

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Purpose This study evaluated the change (Δ) in plasma volume (PV), nitrate [NO3−], and nitrite [NO2−] concentration following changes in posture in the presence and absence of elevated plasma [NO3−] and [NO2−] Methods Fourteen healthy participants completed two trials that were preceded by either supplementation with NO3−-rich beetroot juice (BR; total of ∼31 mmol NO3−) or no supplementation (CON). Both trials comprised 30 min of lying supine followed by 2 min of standing, 2 min of sitting and 5 min of sub-maximal cycling. Measurements of plasma [NO3−] and [NO2−] were made by gas-phase chemiluminescence and ΔPV was estimated using the Dill and Costill method. Results Plasma [NO2−] decreased from baseline (CON: 120 ± 49 nM, BR: 357 ± 129 nM) after lying supine for 30 min (CON 77 ± 30 nM; BR 231 ± 92 nM, both P < 0.01) before increasing during standing (CON 109 ± 42 nM; BR 297 ± 105 nM, both P < 0.01) and sitting (CON 131 ± 43 nM; BR 385 ± 125 nM, both P < 0.01). Plasma [NO2−] remained elevated following exercise only in CON (125 ± 61 nM P = 0.02). Plasma [NO3−] was not different between measurement points in either condition (P > 0.05). PV increased from baseline during the supine phase before decreasing upon standing, sitting, and exercise in both trials (all P<0.05). Conclusions Changing body posture causes rapid and consistent alterations in plasma [NO2−]. Researchers should therefore carefully consider the effect of posture when measuring this variable.

Item Type: Article
Additional Information: © 2018 Elsevier. This is an author accepted manuscript of a paper subsequently published in Nitric Oxide. Uploaded in accordance with the publisher's self-archiving policy
Depositing User: Luke Liddle
Date Deposited: 10 Sep 2019 13:57
Last Modified: 10 Sep 2019 13:57

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