| 1. |
- Van Wert, Jacey C, et al.
(author)
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Coronary circulation enhances the aerobic performance of wild Pacific salmon.
- 2024
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In: The Journal of experimental biology. - 1477-9145.
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Journal article (peer-reviewed)abstract
- Female Pacific salmon often experience higher mortality than males during their once-in-a-lifetime up-river spawning migration, particularly when exposed to secondary stressors (e.g. high temperatures). However, the underlying mechanisms remain unknown. One hypothesis is that female Pacific salmon hearts are more oxygen-limited than males and are less able to supply oxygen to the body's tissues during this demanding migration. Notably, female hearts have higher coronary blood flow, which could indicate a greater reliance on this oxygen source. Oxygen limitations can develop from naturally occurring coronary blockages (i.e., coronary arteriosclerosis) found in mature salmon hearts. If female hearts rely more heavily on coronary blood flow but experience similar arteriosclerosis levels as males, they will have disproportionately impaired aerobic performance. To test this hypothesis, we measured resting (RMR) and maximum metabolic rate (MMR), aerobic scope (AS) and acute upper thermal tolerance in coho salmon (Oncorhynchus kisutch) with an intact or artificially blocked coronary oxygen supply. We also assessed venous blood oxygen and chemistry (cortisol, ions, and metabolite concentrations) at different time intervals during recovery from exhaustive exercise. We found that coronary blockage impaired MMR, AS, and the partial pressure of oxygen in venous blood (PvO2) during exercise recovery but did not differ between sexes. Coronary ligation lowered acute upper thermal tolerance by 1.1°C. Though we did not find evidence of enhanced female reliance on coronary supply, our findings highlight the importance of coronary blood supply for mature wild salmon, where migration success may be linked to cardiac performance, particularly during warm water conditions.
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| 2. |
- Zena, Lucas, 1984, et al.
(author)
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Ischemia-induced alterations in the electrocardiogram of salmonid fish
- 2024
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In: AQUACULTURE. - 0044-8486 .- 1873-5622. ; 581
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Journal article (peer-reviewed)abstract
- Cardiovascular diseases such as coronary arteriosclerosis are widespread and constitute severe health and welfare problems for both farmed and wild salmonid fish. However, effective tools for rapid screening and analysing heart diseases in fish do not currently exist. Electrocardiogram (ECG) recordings are widely used for screening and diagnosing numerous cardiac pathologies in humans, but the use of ECG techniques to diagnose and characterize cardiac abnormalities in fish is still in its infancy. In this study, we induced myocardial ischemia in anaesthetized rainbow trout by surgical coronary artery ligation. Additionally, we experimentally manipulated the fish's heart rate and environmental oxygen availability by altering gill water flow and oxygen saturation (i.e., no flow, normoxic flow and hyperoxic flow), and analyzed changes in the ECG profile in detail. The main ECG abnormalities observed in fish with ligated coronaries in normoxia were atrioventricular blocks, prolonged QRS duration, reduced QRS amplitude and changes in the ST-segment such as the presence of early repolarization pattern. Furthermore, when gill water flow was stopped, fish exhibited pronounced hypoxic bradycardia, which alleviated all ECG abnormalities in coronary ligated fish. This is the first study to provide a detailed characterization of electrocardiographic markers of myocardial ischemia in fish. Our study shows that hypoxic bradycardia improves cardiac electrical conductivity, presumably by reducing mismatches in myocardial oxygen supply and demand. Yet, the importance of avoiding hypoxic bradycardia in experimental and biomedical studies on anaesthetized fish is highlighted as it can potentially lead to incorrect ECG interpretations.
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