Journal
BIOLOGY LETTERS
Volume 18, Issue 11, Pages -Publisher
ROYAL SOC
DOI: 10.1098/rsbl.2022.0401
Keywords
hyperoxia; O-2 supersaturation; aerobic scope; cardiac output; exhaustive exercise; oxygen consumption
Categories
Funding
- Wenner-Gren Foundations [UPD2019-0159]
- Swedish Research Council (Vetenskapsradet) [2019-00299, 2018-00516]
- Swedish Research Council [2018-00516, 2019-00299] Funding Source: Swedish Research Council
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The study demonstrates that hyperoxia can increase maximal oxygen consumption rate in rainbow trout, achieved through increased cardiac output and arterial-venous oxygen content difference. Hyperoxia protects arterial oxygenation, leading to higher arterial oxygen content and A-V O-2 content difference post-exercise.
Several studies have demonstrated that hyperoxia increases the maximal O-2 consumption rate (<(M) over dot>O-2max) in fish, but exactly how this occurs remains to be explained. Here, we tested the hypothesis that hyperoxia improves arterial oxygenation in rainbow trout during exhaustive exercise. We demonstrate a 35% higher <(M) over dot>O-2max in hyperoxia (200% air saturation) relative to normoxia, which was achieved through a combined 15% increase in cardiac output due to elevated peak heart rate, and a 19% increase of the arterial-venous (A-V) O-2 content difference. While arterial O-2 partial pressure (PaO2) and O-2 saturation of haemoglobin declined post-exhaustive exercise in normoxia, this did not occur in hyperoxia. This protective effect of hyperoxia on arterial oxygenation led to a 22% higher arterial O-2 content post-exhaustive exercise, thereby allowing a higher A-V O-2 content difference. These findings indicate that <(M) over dot>O-2max is gill diffusion limited in exhaustively exercised rainbow trout. Moreover, as previous studies in salmonids have demonstrated collapsing PaO2 in normoxia at maximal swimming speed and at acutely high temperatures, a diffusion limitation may constrain <(M) over dot>O-2 in other situations eliciting peak metabolic demand. These findings, along with the fact that hyperoxia increases <(M) over dot>O-2max in several other fishes, suggest that gill diffusion limitations of <(M) over dot>O-2max may be widespread in fishes.
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