1. Radiotracer and cannulation techniques have been used to measure branchial fluxes and internal distributions of sodium in freshwater adapted rainbow trout at rest, during one hour of swimming activity, and during one hour of postexercise recovery. 2. Activity was imposed by manual chasing in a small chamber. Ventilatory and cardiovascular changes occurring during and after this procedure were similar to those associated with normal swimming. 3. Sodium efflux rate equalled influx at rest, increased 70% during exercise, and returned to slightly below resting levels during recovery; influx rate remained invariant under the three treatments. The switch from a negative to a positive branchial sodium balance at the end of exercise occurred extremely rapidly. 4. Despite the branchial deficit, plasma sodium levels tended to rise in active fish. This effect was associated with an apparent reduction in blood volume. 5. Terminal concentrations of sodium and water in "white" muscle did not differ significantly among treatment groups. 6. Expansion of the radiosodium space in active and recovering trout exceeded that in resting animals because of a faster rate of dispersal of influxed sodium out of the plasma compartment into tissues other than "white" muscle.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology
- Behavioral Neuroscience