Velocity of oxygen uptake by red cells of the rainbow trout ( Salmo gairdneri) at different temperatures

Abstract

1. 1. The velocity constant for oxygen uptake by deoxy red blood cells of the rainbow trout ( Salmo gairdneri) was measured in a stopped-flow apparatus at 5, 13 and 22°C. The cells were suspended in saline-phosphate buffer with no bicarbonate. No CO 2 was present in equilibrating gases and pH was alkaline enough to keep the Root effect below 5%. 2. 2. The nine fish studied fell into two groups—those studied in summer (slower reacting) and those studied in autumn or winter (faster reacting). 3. 3. The values of k c' at 22°C were 60 and 78 per mM per sec, respectively, in these groups. 4. 4. The activation energies were 7.1 and 6.7 kcal/mol respectively, Q 10 being 1.5 in the range studied. When the reaction rate was expressed as θ, where the uptake is per Torr P O 2 gradient with the red cells, activation energy was lower, 3.6 and 3.1 kcal/mol, respectively. 5. 5. The values for θ indicate that reaction rates are unlikely to limit oxygen uptake in the gills.