Inter Relationship between Acid Base, Ionic and Water Balance in RainbowTrout (Salmo gairdneri) Exercised until Fatigue Occurred

Abstract

Rainbow trout (Salmo gairdneri) were exercised at greater than 3.5 Ijsec until fatigue occurred. Severe exercise induced marked disturbances ;n acid base, ionic and water balance. Immediately after fatigue the drop in pH was due to the combined effects of increased Pe02 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 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 lOA mequtvl). A rapid increase in plasma volume during recovery following fatigue was accompanied by increases In total Na+ and C 1- contents of over 50% of the respective resting values. This increase in Na+ and CIcontents occurred presumably via branchial Na+ /H+ and CI-/HCO-) 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 CI - / 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 +.