The effect of adrenaline and high Ca on the mechanical performance and oxygen consumption of the isolated perfused trout (Oncorhynchus mykiss) heart

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2007-08, Vol.147 (4), p.1083-1089
• Main Authors: Rytter, D, Gesser, H
• Format: Article
• Language: English
• Subjects: Brackish; Freshwater; Marine; Oncorhynchus mykiss
• ISSN: 1095-6433
• DOI: 10.1016/j.cbpa.2007.03.031

In heart muscle from mammals, catecholamines frequently evoke an oxygen waste and reduce efficiency. It was examined if this also applies to fish in which heart muscle activity is often restricted by oxygen availability. In the isolated perfused heart from rainbow trout, adrenaline (0.5 mu M) increased power output by 97%, when afterload was adjusted to maximum both before and after adrenaline addition, and by 68%, when afterload remained at the maximum obtained before adrenaline addition. Oxygen consumption was enhanced by a similar amount (70%) in both situations. Hence, efficiency, i.e. power output/oxygen consumption, increased significantly from 25 to 30% for the heart always exposed to maximal afterload, whereas it stayed unchanged at 24% for the heart exposed to control afterload only. Adrenaline increases the Ca2+activity participating in activation, but doing this by elevating perfusate Ca2+from 1.5 to 5mM instead of applying adrenaline did not change the mechanical efficiency, although afterload was maximized. The results suggest that catecholamines enhance heart pump activity in the living trout without any oxygen waste. On the contrary, the oxygen budget may even improve when the peripheral resistance is increased by catecholamines.