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

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 ...