The Effect of Cortisol on Recovery from Exhaustive Exercise in Rainbow Trout (Oncorhynchus mykiss): Potential Mechanisms of Action

1996 ◽  
Vol 69 (5) ◽  
pp. 1196-1214 ◽  
Author(s):  
Steve K. Eros ◽  
C. Louise Milligan
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Mechanisms Of Action ◽  
Exhaustive Exercise ◽  
Rainbow Trout Oncorhynchus Mykiss

scholarly journals Normoxic limitation of maximal oxygen consumption rate, aerobic scope and cardiac performance in exhaustively exercised rainbow trout (Oncorhynchus mykiss)

2021 ◽  
Author(s):  
T.J. McArley ◽  
D. Morgenroth ◽  
L.A. Zena ◽  
A.E. Ekström ◽  
E. Sandblom
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Consumption Rate ◽  
Venous Blood ◽  
Cardiac Contractility ◽  
Cardiac Performance ◽  
Exhaustive Exercise ◽  
Aerobic Scope ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
O2 Supply

In fish, maximum O2 consumption rate (MO2max) and aerobic scope can be expanded following exhaustive exercise in hyperoxia; however, the mechanisms explaining this are yet to be identified. Here, in exhaustively exercised rainbow trout (Oncorhynchus mykiss), we assessed the influence of hyperoxia on MO2max, aerobic scope, cardiac function and blood parameters to address this knowledge gap. Relative to normoxia, MO2max was 33% higher under hyperoxia, and this drove a similar increase in aerobic scope. Cardiac output, due to increased stroke volume, was significantly elevated under hyperoxia at MO2max indicating hyperoxia released a constraint on cardiac contractility apparent with normoxia. Thus, hyperoxia improved maximal cardiac performance, thereby enhancing tissue O2 delivery and allowing a higher MO2max. Venous blood O2 partial pressure (PvO2) was elevated in hyperoxia at MO2max, suggesting a contribution of improved luminal O2 supply in enhanced cardiac contractility. Additionally, despite reduced haemoglobin and higher PvO2, hyperoxia treated fish retained a higher arterio-venous O2 content difference at MO2max. This may have been possible due to hyperoxia offsetting declines in arterial oxygenation known to occur following exhaustive exercise in normoxia. If this occurs, increased contractility at MO2max with hyperoxia may also relate to an improved O2 supply to the compact myocardium via the coronary artery. Our findings show MO2max and aerobic scope may be limited in normoxia following exhaustive exercise due to constrained maximal cardiac performance and highlight the need to further examine whether or not exhaustive exercise protocols are suitable for eliciting MO2max and estimating aerobic scope in rainbow trout.

The role of blood glucose in the restoration of muscle glycogen during recovery from exhaustive exercise in rainbow trout (Oncorhynchus mykiss) and winter flounder (Pseudopleuronectes americanus)

1991 ◽  
Vol 161 (1) ◽  
pp. 489-508 ◽  
Author(s):  
A. Pagnotta ◽  
C. L. Milligan
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Muscle Glycogen ◽  
Extracellular Fluid ◽  
Winter Flounder ◽  
Exhaustive Exercise ◽  
Pseudopleuronectes Americanus ◽  
Post Exercise ◽  
Rainbow Trout Oncorhynchus Mykiss

The role of blood-borne glucose in the restoration of white muscle glycogen following exhaustive exercise in the active, pelagic rainbow trout (Oncorhynchus mykiss) and the more sluggish, benthic winter flounder (Pseudopleuronectes americanus) were examined. During recovery from exhaustive exercise, the animals were injected with a bolus of universally labelled [14C]glucose via dorsal aortic (trout) or caudal artery (flounder) catheters. The bulk of the injected label (50–70%) remained as glucose in the extracellular fluid in both species. The major metabolic fates of the injected glucose were oxidation to CO2 (6–8%) and production of lactate (6–8%), the latter indicative of continued anaerobic metabolism post-exercise. Oxidation of labelled glucose could account for up to 40% and 15% of the post-exercise MO2 in trout and flounder, respectively. Exhaustive exercise resulted in a reduction of muscle glycogen stores and accumulation of muscle lactate. Glycogen restoration in trout began 2–4h after exercise, whereas in flounder, glycogen restoration began within 2h. Despite a significant labelling of the intramuscular glucose pool, less than 1% of the infused labelled glucose was incorporated into muscle glycogen. This suggests that blood-borne glucose does not contribute significantly to the restoration of muscle glycogen following exhaustive exercise in either trout or flounder and provides further evidence against a prominent role for the Cori cycle in these species.

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