The role of intermediary metabolism in the maintenance of proton and charge balance during exercise.

The purpose of this investigation was to examine the role of intermediary metabolism in the maintenance of proton and charge balance in rainbow trout white muscle during exercise. With increasing power outputs, there was a greater reliance on white fibers and anaerobic processes for energy production. Glycogen content declined from a pre-exercise (pre-ex) level of 23 to less than 1 mumol/g following the exhaustive swim, with its greatest rate of decline occurring during the burst swim. Lactate accumulation reached a maximum of 43 mumol/g during the exhaustive swim. PCr declined from about 20 to less than 2 mumol/g at exhaustion with a concomitant accumulation of Cr. ATP decreased from about 7.3 to 2.7 mumol/g while inorganic phosphate and IMP increased to about 56 and 4.3 mumol/g, respectively. The intramuscular pH fell from 6.97 to 6.93 during the sustained swim, declining further to 6.65 during the burst swim and reaching a minimum of 6.56 at exhaustion. Exercise induced depletions of high energy compounds and accumulations of metabolic end products nearly stabilized the accompanying intracellular perturbations in charge and proton levels. Compensatory shifts in Na+, K+ and Cl- served to negate the residual imbalances such that electrical neutrality, membrane potential and pH were preserved.