Inter relationships between acid base. ioniC:and water balance in Rainbow Trout (Salmo gairdneri) exercised until fatigue occurred

Abstract

Rainbow trout (Salmo gairdneri) were exercised at greater than 3.5
1/sec until fatigue occurred. Severe exercise induced marked disturbances in acid base, ionic and water balance. Immediately after fatigue the
drop in pH was due to the combined effects of increased PC02 and metabolic acid. But the bulk of the increase in H+ buffered by blood was caused by an increase in metabolic acid. The peak in this contribution, occurring at 1 hour post exercise corresponded to the peak lactate concentration.
However, there was a considerable quantitative discrepancy between I H+I
and I L- I. At 2 hours post exercise I L- I exceeded I H+ I by a maximum
volue of l0.4 mequiv/l).
A rapid increase in plasma volume during recovery following fatigue
was accompanied by increases In total Na+ and Cl- contents of over
50% of the respective resting values. This increase in Na+ and CIcontents
occurred presumably via branchial Na+ /H+ and CI-/HCO 3-
ion exchange mechanis ms.
It seems most likely that a large portion of the metabolic protons
found ln deficit in blood during recovery was eliminated into the
environmental water through appropriate adjustment of Na+ / H + and
Cl - / HCO 3 - exchanges [unctioning at the gill epithelium. The rest
of the metabolic protons contributing to the deficit were most likely
exchanged for intracellular K +.