Effects of exercise training and coronary ablation on swimming performance, heart size, and cardiac enzymes in rainbow trout, Oncorhynchus mykiss

Abstract

Rainbow trout, Oncorhynchus mykiss, were exercise trained for 28–52 days. Trained fish were 13% larger and swam 12% faster in an aerobic swimming test. Training induced cardiac growth that was isometric with body growth, since ventricle mass relative to body mass was constant. The proportions of compact and spongy myocardia in the ventricle were also unchanged by training. Trained fish had significantly higher levels of citrate synthase, β-hydroxyacyl CoA dehydrogenase, and hexokinase in both compact and spongy myocardium. Ligation of a 0.5- to 1.0-cm section of the coronary artery produced only a temporary interruption of coronary flow to the compact myocardium because new vessels grew around the ligation site in the majority of fish during the 28- to 52-day experiment. Nonetheless, coronary ligation resulted in a significantly smaller (17%) proportion of compact myocardium with lower levels of citrate synthase, β-hydroxyacyl CoA dehydrogenase, and hexokinase. Exercise-induced increases in the levels of these enzymes in the compact myocardium were prevented by coronary ligation. The decrease of enzymes in the compact myocardium as a result of coronary ligation was compensated for by a 30% increase in the levels of the aerobic enzymes citrate synthase and β-hydroxyacyl CoA dehydrogenase and a 32% increase in the mass of spongy myocardium. As a result of these compensations and coronary regrowth, chronic coronary ligation did not affect maximum prolonged swimming speed. These experiments clearly reveal that cardiac plasticity allows compensatory changes that are necessary for the heart to maintain adequate oxygen delivery to exercising skeletal muscle. The compensatory changes were isometric increases in heart mass or proportionately larger increases in heart mass and compact tissue if the coronary artery was ligated and an increase in metabolic enzymes associated with ATP generation, namely, citrate synthase, β-hydroxyacyl CoA dehydrogenase, and hexokinase.

Fast water currents reduce production performance of post-smolt Atlantic salmon Salmo salar

“…This result is in line with previous studies on exercised salmonids (Gallaugher et al 2001, Castro et al 2013, even considering differences in setup, although exceptions do exist (Farrell et al 1990). The increase in heart size is most likely related to an increased cardiac workload during sustained swimming through an increase in aerobic respiration.…”

“…Reduced ATP depletion after fatigue challenge and increased energy stores in muscle occurs in rainbow trout Oncorhynchus mykiss as an effect of exercise (Pearson et al 1990, McFarlane & McDonald 2002. Other positive effects of exercise include increased cardiac output (Farrell et al 1991), ventricular mass (Gallaugher et al 2001, Castro et al 2013, intestinal blood flow (Thorarensen et al 1993), maximum metabolic rate ) and swimming performance (Farrell et al 1990, Pearson et al 1990). There are also indications that exercise generates a more robust fish with a higher ability to cope with different challenges, such as pathogens (Castro et al 2011).…”

Oxygen- and capacity-limited thermal tolerance: bridging ecology and physiology

“…Active fishes usually have a larger relative heart mass (Santer, 1985;Farrell, 1991). Accordingly, exercise training can produce isometric cardiac growth as seen in rainbow trout (Farrell et al, 1990). Cardiac output depends on the volume of the heart and the pressure generated by wall tension.…”

The effect of acclimation to hypoxia and sustained exercise on subsequent hypoxia tolerance and swimming performance in goldfish (Carassius auratus)

“…At swimming velocities approaching U crit , the metabolic demand for oxygen may be greater than that which can be provided by the cardio-respiratory system, just as would occur in hypoxic conditions (Jones and Randall, 1978). Likewise, exercise training in fish may also alter components of the cardio-respiratory system, for example, resulting in larger hearts or higher pumping performance (Hochachka, 1961;Farrell et al, 1990;Gamperl and Farrell, 2004), higher Hb and myoglobin concentration (Holk and Lykkeboe, 1998), and increased skeletal muscle capillarity and tissue O 2 extraction (Love et al, 1977;Gamperl and Farrell, 2004). An increase in M O2,max and U crit has been observed after exercise training in rainbow trout (Oncorhynchus mykiss) (Holk and Lykkeboe, 1998), darkbarbel catfish (Peltebagrus vachelli) (Liu et al, 2009;Li et al, 2010) and striped bass (Morone saxatilis) (Young and Cech, 1993;Young and Cech, 1994); however, they have not previously been investigated in goldfish.…”