Organization of energy provision in rainbow trout during exercise
Parkhouse, W.S.; Dobson, G.P.; Hochachka, P.W.
American Journal of Physiology 254(2 Pt 2): R302-R309
1988
ISSN/ISBN: 0002-9513 PMID: 3344838 Document Number: 315380
The fuels supporting high-intensity progressive exercise and their regulation were studied in rainbow trout. During the sustained swim, red muscle (RM) used 97% (17.5 micro mol/g) of its glycogen, whereas white muscle (WM) glycogen only declined 31% (7.3 micro mol/g). During a burst swim, WM glycogen content decreased 10.4 micro mol/g at a rate that exceeded the sustained swim rate by 6.2-fold. Lactate content increased 11-fold at a rate 25 times its sustained swim rate. An exhaustive swim resulted in a decrease of 36.6 micro mol/g in liver glycogen, whereas WM glycogen content declined to low values and lactate reached 43 micro mol/g. RM glycogen values remained low during these exercise bouts. Phosphocreatine (PCr)-buffered ATP decreased (WM 7.3 to 2.7 micro mol/g, RM 3.4 to 1.6 micro mol/g) with the time course of the large ATP decreases related to near depletion of PCr. Decreases in the total adenylate pool were compensated for by the accumulation of inosine 5' -monophosphate in both tissue types. Free ADP (ADPf) contents increased in both tissues by three- to fivefold. ATP/ADPf and cytosolic phosphorylation potentials decreased. Cytosolic redox potential remained relatively constant at about 145 within both fibre types. The changes in adenine nucleotide indices are associated with the respective activation of the different fibre types and glycolytic flux.