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Research article - Peer-reviewed, 2022

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

Morgenroth, Daniel; McArley, Tristan; Ekstrom, Andreas; Grans, Albin; Axelsson, Michael; Sandblom, Erik


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 (R-Sys and R-GI, 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 (1/2 SW, similar to 17 ppt) to control fish (i.e., no perfusion). We show that perfusion with 1/2 SW causes significantly larger increases in CO, SV and GBF, as well as reductions in R-Sys and R-GI, 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.


Gastrointestinal sensing mechanisms; Vascular resistance; Blood flow; Salinity

Published in

Journal of Comparative Physiology B :: Biochemical, Systemic, and Environmental Physiology
2022, volume: 192, number: 1, pages: 95-106

Authors' information

Morgenroth, Daniel
University of Gothenburg
McArley, Tristan
University of Gothenburg
Ekstrom, Andreas
University of Gothenburg
Swedish University of Agricultural Sciences, Department of Animal Environment and Health
Axelsson, Michael
University of Gothenburg
Sandblom, Erik
University of Gothenburg

UKÄ Subject classification

Fish and Aquacultural Science

Publication Identifiers


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