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. 2021 Jan 7:11:609642.
doi: 10.3389/fphys.2020.609642. eCollection 2020.

Nitric Oxide and Oxidative Stress Changes at Depth in Breath-Hold Diving

Danilo Cialoni  1   2   3 , Andrea Brizzolari  2   4 , Michele Samaja  4 , Gerardo Bosco  1 , Matteo Paganini  1 , Massimo Pieri  2 , Valentina Lancellotti  5 , Alessandro Marroni  2
Affiliations

Nitric Oxide and Oxidative Stress Changes at Depth in Breath-Hold Diving

Danilo Cialoni et al. Front Physiol. .

Abstract

Background: Several mechanisms allow humans to resist the extreme conditions encountered during breath-hold diving. Available nitric oxide (NO) is one of the major contributors to such complex adaptations at depth and oxidative stress is one of the major collateral effects of diving. Due to technical difficulties, these biomarkers have not so far been studied in vivo while at depth. The aim of this study is to investigate nitrate and nitrite (NOx) concentration, total antioxidant capacity (TAC) and lipid peroxidation (TBARS) before, during, and after repetitive breath-hold dives in healthy volunteers.

Materials and methods: Blood plasma, obtained from 14 expert breath-hold divers, was tested for differences in NOx, TAC, and TBARS between pre-dive, bottom, surface, 30 and 60 min post-dive samples.

Results: We observed a statistically significant increase of NOx plasma concentration in the "bottom blood draw" as compared to the pre-dive condition while we did not find any difference in the following samples We found a statistically significant decrease in TAC at the bottom but the value returned to normality immediately after reaching the surface. We did not find any statistically significant difference in TBARS.

Discussion: The increased plasma NOx values found at the bottom were not observed at surface and post dive sampling (T0, T30, T60), showing a very rapid return to the pre-dive values. Also TAC values returned to pre- diving levels immediately after the end of hyperbaric exposure, probably as a consequence of the activation of endogenous antioxidant defenses. TBARS did not show any difference during the protocol.

Keywords: breath-hold diving; diving; free radicals; nitric oxide; oxidative stress.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Description of protocol in the swimming pool Y-40. Basal, 30 min before; Bottom, at −42 m; T0, On arrival at the surface; T30, 30 min after; T60, 60 min after.
FIGURE 2
FIGURE 2
NOx changes, compared to the pre value, showed a statistically significant increase at the bottom p < 0.0001 while no differences were found in the follow-up. ***Significative differences p < 0.001.
FIGURE 3
FIGURE 3
TAC changes, compared to the pre value, showed a statistically significant decreases at the bottom p < 0.0001, no differences were found in the follow-up. ***Significative differences p < 0.001.
FIGURE 4
FIGURE 4
No changes between pre and post BH-diving training session were found about TBARS.
See this image and copyright information in PMC

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