Milligan, C.L (1997). The role of cortisol
in amino acid mobilization and metabolism following exhaustive
exercise in rainbow trout (Oncorhynchus mykiss Walbaum).
Fish Physiology and Biochemistry. 16 (2) 119-128.
The role of cortisol in
the mobilization and metabolism of amino acids following exhaustive
exercise in rainbow trout (Oncorhynchus mykiss) was investigated.
Plasma cortisol levels were elevated for 4h following exercise
and 6, of a total of 22 amino acids, showed significant responses.
In white muscle, alanine and glutamine were elevated immediately
after exercise through to 4 h, whereas glutamate, and the branched-chain
amino acids (BCAA), isoleucine, leucine and valine, all decreased
over this time. In plasma all of these amino acids increased from
2-4 h post-exercise, while in liver, alanine and glutamine increased,
glutamate did not change and the BCAAs declined over this time.
Blockade of the post-exercise elevation in plasma cortisol with
either metyrapone (cortisol synthesis inhibitor) or dexamethasone
(cortisol release blocker) prevented the changes in tissue amino
acid levels. This study demonstrates that cortisol can act rapidly
(within minutes to hours) to alter amino acid metabolism in fish.
A model is presented to explain the action of cortisol on amino
acid metabolism.