title: Cardiac remodeling and increased central venous pressure underlie elevated stroke volume and cardiac output of seawater-acclimated rainbow trout.
abstract: Substantial increases in cardiac output (CO), stroke volume (SV), and gastrointestinal blood flow are essential for euryhaline rainbow trout (Oncorhyncus mykiss) osmoregulation in seawater. However, the underlying hemodynamic mechanisms responsible for these changes are unknown. By examining a range of circulatory and cardiac morphological variables of seawater- and freshwater-acclimated rainbow trout, the present study revealed a significantly higher central venous pressure (CVP) in seawater-acclimated trout (~0.09 vs. -0.02 kPa). This serves to increase cardiac end-diastolic volume in seawater and explains the elevations in SV (~0.41 vs. 0.27 ml/kg) and CO (~21.5 vs. 14.2 ml·min-1·kg-1) when compared with trout in freshwater. Furthermore, these hemodynamic modifications coincided with a significant increase in the proportion of compact myocardium, which may be necessary to compensate for the increased wall tension associated with a larger stroke volume. Following a temperature increase from 10 to 16.5°C, both acclimation groups exhibited similar increases in heart rate (Q10of ~2), but SV tended to decrease in seawater-acclimated trout despite the fact that CVP was maintained in both groups. This resulted in CO of seawater- and freshwater-acclimated trout stabilizing at a similar level after warming (~26 ml·min-1·kg-1). The consistently higher CVP of seawater-acclimated trout suggests that factors other than compromised cardiac filling constrained the SV and CO of these individuals at high temperatures. The present study highlights, for the first time, the complex interacting effects of temperature and water salinity on cardiovascular responses in a euryhaline fish species.
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden; jeroen.brijs@bioenv.gu.se.
authors.forename: Jeroen
authors.identifier: 0000-0002-3671-5038
authors.initials: J
authors.lastname: Brijs
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Sandblom
authors.affiliation: Institute for Life Sciences and Chemistry, University of Applied Sciences, Utrecht, The Netherlands; and.
authors.forename: Esmée
authors.initials: E
authors.lastname: Dekens
authors.affiliation: Faculty of Science, Department of Ecosystem Biology, University of South Bohemia, České Budějovice, Czech Republic.
authors.forename: Joacim
authors.initials: J
authors.lastname: Näslund
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ekström
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Axelsson
mesh_terms: D000818:Animals; D002302:Cardiac Output / Q000502:physiology*; D002496:Central Venous Pressure / Q000502:physiology*; D017686:Oncorhynchus mykiss / Q000502:physiology*; D064587:Osmoregulation / Q000502:physiology; D055049:Salt Tolerance / Q000502:physiology*; D012623:Seawater; D013318:Stroke Volume / Q000502:physiology*; D020257:Ventricular Remodeling / Q000502:physiology
keywords: cardiac filling pressure; cardiovascular; circulation; osmoregulation; venous capacitance; venous tone