An analysis of carbon dioxide transport in arterial and venous blood of the rainbow trout, Oncorhynchus mykiss, following exhaustive exercise.

Arterial and venous cannulations were used to examine the characteristics of CO2 transport in pre and post branchial blood both at rest and during recovery from exercise. As in previous studies, exercise caused a marked decrease in the extracellular pH (pHe) in both arterial and venous blood. Except for a transient increase in venous blood immediately following exercise, plasma total CO2 ([CCO 2]pl) and whole blood total CO2 ([CCO 2]wb) decreased in both arterial and venous blood during recovery. Exercise also resulted in an increase in red blood cell total CO2 concentration ([CCO 2]i) and in the partial pressure of CO2 (PCO 2) in both arterial and venous blood. Activation of the adrenergic mechanism at the level of the red blood cell likely contributed to the increases observed in ([CCO 2]i) following exercise. At rest, the majority of the total [CCO 2] carried in arterial and venous blood could be attributed to the plasma, with 2 and 9% carried in the red blood cells, respectively. However, exercise resulted in an increase in the percentage of C02 carried within the red blood cell to 13.5 and 20% in arterial and venous blood, respectively. The total CO2 difference between pre and post branchial blood also increased following exercise suggesting an increase in CO2 excretion.