Relationships between swimming speed, oxygen consumption, plasma catecholamines and heart performance in rainbow...

Rainbow trout swimming at controlled speeds in a tunnel respirometer have been used to measure oxygen consumption and plasma catecholamine levels, and systolic pressure/frequency relationships. Catecholamine (CA) levels evaluated in trout plasma at low swimming speed [0.5 bodylengths/second (bl/s)] were: adrenaline (A) 1.77 +/- 0.22 nM; noradrenaline (NA) 3.94 +/- 0.83 nM; dopamine (DA) 2.40 +/- 0.36 nM. No significant increase was observed during moderate exercise (1.5 bl/s): A 1.60 +/- 0.20 nM; NA 5.76 +/- 1.07 nM; DA 2.31 +/- 0.80 nM, or stronger exercise (2.0 and 2.5 bl/s-1): A 2.10 +/- 0.21 nM; NA 5.90 +/- 0.90 nM; DA 2.21 +/- 0.40 nM. A correlation was found between heart rate at these swimming speeds, and its position on the systolic pressure frequency curve of isolated hearts, which suggests that the heart functions at maximum systolic pressure at low (0.5 bl/s-1) swimming speeds and that this pressure decreases during exercise as cardiac frequency rises.