Seawater acclimation affects cardiac output and adrenergic control of blood pressure in rainbow trout (<i>Oncorhynchus mykiss</i>)—implications for salinity variations now and in the future

Sundell, Erika; Morgenroth, Daniel; Brijs, Jeroen; Ekström, Andreas; Gräns, Albin; Sandblom, Erik

doi:10.1093/conphys/coy061

Cited by 8 publications

(17 citation statements)

References 62 publications

(81 reference statements)

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“…The reduced Pa and increased cardiac output in SW-acclimated fish prior to warming in the two experimental series of the present study suggests a reduced systemic vascular resistance in SW. This, corroborates the findings of Sundell et al (2018) who measured arterial pressure and cardiac output in the same fish at different acclimation salinities. Moreover, using the calculated absolute GBF at 11°C, it appears that a substantially higher proportion of cardiac output was directed to the gastrointestinal tract in SW fish (42% of cardiac output) compared to FW trout (25% of cardiac output).…”

Section: Vascular Resistance Dictates Gastrointestinal Blood Flow Acrsupporting

confidence: 91%

“…Moreover, using the calculated absolute GBF at 11°C, it appears that a substantially higher proportion of cardiac output was directed to the gastrointestinal tract in SW fish (42% of cardiac output) compared to FW trout (25% of cardiac output). Taking into account the reduced blood pressure and systemic vascular resistance in SW-acclimated trout (Sundell et al, 2018), this suggests that reduced gastrointestinal vascular resistance and not elevated arterial blood pressure explains the elevated gastrointestinal blood flow of SW trout. However, the lower Pa in SW-acclimated trout may also be partly attributed to reduced blood volume, as previously reported by Olson and Hoagland (2008).…”

Section: Vascular Resistance Dictates Gastrointestinal Blood Flow Acrmentioning

confidence: 95%

“…For all surgical protocols and acclimation groups, fish were anesthetized in FW containing 150 mg l −1 MS222 (ethyl-3-aminobenzoate methanesulphonic acid, Sigma-Aldrich Inc., St Louis, MO, USA) buffered with 300 mg l −1 NaHCO 3 (see Sundell et al, 2018). Once the opercular movements ceased, body length and mass were determined and the fish was placed on a surgical table covered with wet foam.…”

Section: Surgery and Instrumentationmentioning

confidence: 99%

“…As the SW-acclimated fish had a significantly lower [hemoglobin] and higher cardiac output, this likely reflects a decreased tissue O 2 extraction in SW trout. This could also explain why some studies have reported little or no change in O 2 consumption with SW acclimation (Brijs et al, 2015;Ern et al, 2014), despite substantial increases in cardiac output (Maxime et al, 1991;Sundell et al, 2018). To better substantiate this hypothesis, simultaneous measurements of arterial and venous O 2 content of fish in both salinities would be required.…”

Section: Cardiac Function Is Maintained In Sw-acclimated Trout Acrossmentioning

confidence: 99%

“…This mechanism is thought to sustain an elevated demand for nutrients and O 2 in the gastrointestinal tissues as osmoregulatory function increases, as well as to transport absorbed ions to their respective sites of excretion at the gills and kidneys (Brijs et al, 2015(Brijs et al, , 2016. Chronically SW-acclimated trout also have an elevated stroke volume and cardiac output (Brijs et al, 2016(Brijs et al, , 2017Sundell et al, 2018), which is at least partially due to increased end-diastolic cardiac filling (Frank-Starling mechanism), as indicated by an elevated central venous blood pressure in SW (Brijs et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Hemodynamic responses to warming in euryhaline rainbow trout -implications of the osmo-respiratory compromise

Morgenroth

Ekström

Hjelmstedt

et al. 2019

Journal of Experimental Biology

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In seawater, rainbow trout (Oncorhynchus mykiss) drink and absorb water through the gastrointestinal tract to compensate for water passively lost to the hyperosmotic environment. Concomitantly, they exhibit elevated cardiac output and a doubling of gastrointestinal blood flow to provide additional O 2 to the gut and increase convective flux of absorbed ions and water. Yet, it is unknown how warming waters, which elevate tissue O 2 demand and the rate of diffusion of ions and water across the gills (i.e. the osmo-respiratory compromise), affects these processes. We measured cardiovascular and blood variables of rainbow trout acclimated to freshwater and seawater during acute warming from 11 to 17°C. Relative to freshwater-acclimated trout, cardiac output was 34% and 55% higher in seawater-acclimated trout at 11 and 17°C, respectively, which allowed them to increase gastrointestinal blood flow significantly more during warming (increases of 75% in seawater vs. 31% in freshwater). These adjustments likely served to mitigate the impact of warming on osmotic balance, as changes in ionic and osmotic blood composition were minor. Furthermore, seawater-acclimated trout seemingly had a lower tissue O 2 extraction, explaining why trout acclimated to freshwater and seawater often exhibit similar metabolic rates, despite a higher cardiac output in seawater. Our results highlight a novel role of gastrointestinal blood perfusion in the osmo-respiratory compromise in fish, and improve our understanding of the physiological changes euryhaline fishes must undergo when faced with interacting environmental challenges such as transient warming events.

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Section: Vascular Resistance Dictates Gastrointestinal Blood Flow Acrsupporting

confidence: 91%

Section: Vascular Resistance Dictates Gastrointestinal Blood Flow Acrmentioning

confidence: 95%

Section: Surgery and Instrumentationmentioning

confidence: 99%

Section: Cardiac Function Is Maintained In Sw-acclimated Trout Acrossmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hemodynamic responses to warming in euryhaline rainbow trout -implications of the osmo-respiratory compromise

Morgenroth

Ekström

Hjelmstedt

et al. 2019

Journal of Experimental Biology

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Energetic savings and cardiovascular dynamics of a marine euryhaline fish (Myoxocephalus scorpius) in reduced salinity

et al. 2021

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Few studies have addressed how reduced water salinity affects cardiovascular and metabolic function in marine euryhaline fishes, despite its relevance for predicting impacts of natural salinity variations and ongoing climate change on marine fish populations. Here, shorthorn sculpin (Myoxocephalus scorpius) were subjected to different durations of reduced water salinity from 33 to 15 ppt. Routine metabolic rate decreased after short-term acclimation (4–9 days) to 15 ppt, which corresponded with similar reductions in cardiac output. Likewise, standard metabolic rate decreased after acute transition (3 h) from 33 to 15 ppt, suggesting a reduced energetic cost of osmoregulation at 15 ppt. Interestingly, gut blood flow remained unchanged across salinities, which contrasts with previous findings in freshwater euryhaline teleosts (e.g., rainbow trout) exposed to different salinities. Although plasma osmolality, [Na+], [Cl−] and [Ca2+] decreased in 15 ppt, there were no signs of cellular osmotic stress as plasma [K+], [hemoglobin] and hematocrit remained unchanged. Taken together, our data suggest that shorthorn sculpin are relatively weak plasma osmoregulators that apply a strategy whereby epithelial ion transport mechanisms are partially maintained across salinities, while plasma composition is allowed to fluctuate within certain ranges. This may have energetic benefits in environments where salinity naturally fluctuates, and could provide shorthorn sculpin with competitive advantages if salinity fluctuations intensify with climate change in the future.

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Continuous gastric saline perfusion elicits cardiovascular responses in freshwater rainbow trout (Oncorhynchus mykiss)

et al. 2021

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When in seawater, rainbow trout (Oncorhynchus mykiss) drink to avoid dehydration and display stroke volume (SV) mediated elevations in cardiac output (CO) and an increased proportion of CO is diverted to the gastrointestinal tract as compared to when in freshwater. These cardiovascular alterations are associated with distinct reductions in systemic and gastrointestinal vascular resistance (RSys and RGI, respectively). Although increased gastrointestinal blood flow (GBF) is likely essential for osmoregulation in seawater, the sensory functions and mechanisms driving the vascular resistance changes and other associated cardiovascular changes in euryhaline fishes remain poorly understood. Here, we examined whether internal gastrointestinal mechanisms responsive to osmotic changes mediate the cardiovascular changes typically observed in seawater, by comparing the cardiovascular responses of freshwater-acclimated rainbow trout receiving continuous (for 4 days) gastric perfusion with half-strength seawater (½ SW, ~ 17 ppt) to control fish (i.e., no perfusion). We show that perfusion with ½ SW causes significantly larger increases in CO, SV and GBF, as well as reductions in RSys and RGI, compared with the control, whilst there were no significant differences in blood composition between treatments. Taken together, our data suggest that increased gastrointestinal luminal osmolality is sensed directly in the gut, and at least partly, mediates cardiovascular responses previously observed in SW acclimated rainbow trout. Even though a potential role of mechano-receptor stimulation from gastrointestinal volume loading in eliciting these cardiovascular responses cannot be excluded, our study indicates the presence of internal gastrointestinal milieu-sensing mechanisms that affect cardiovascular responses when environmental salinity changes.

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Seawater acclimation affects cardiac output and adrenergic control of blood pressure in rainbow trout (Oncorhynchus mykiss)—implications for salinity variations now and in the future

Cited by 8 publications

References 62 publications

Hemodynamic responses to warming in euryhaline rainbow trout -implications of the osmo-respiratory compromise

Hemodynamic responses to warming in euryhaline rainbow trout -implications of the osmo-respiratory compromise

Energetic savings and cardiovascular dynamics of a marine euryhaline fish (Myoxocephalus scorpius) in reduced salinity

Continuous gastric saline perfusion elicits cardiovascular responses in freshwater rainbow trout (Oncorhynchus mykiss)

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