Abstract
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.
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.
| Original language | English |
|---|---|
| Pages (from-to) | 59-65 |
| Number of pages | 7 |
| Journal | Nitric Oxide |
| Volume | 72 |
| DOIs | |
| Publication status | Published - 30 Jan 2018 |
Keywords
- Beetroot juice
- Exercise
- Plasma volume
