1. Sodium flux rates in the freshwater adapted rainbow trout were measured by radiotracer techniques during longterm swimming (up to 8 hours) and during recovery from extended exercise. 2. Branchial sodium influx rate remained constant under different activity conditions, while whole animal efflux rate was highest during the first hour of swimming (negative sodium balance), declined during the second hour, and reached levels lower than influx rate during the third and subsequent hours of exercise (positive sodium balance). A minimum efflux value occured during the second hour of recovery accompanied by a maximum positive net flux. These changes in efflux rate appeared to be mainly branchial in origin. 3. Branchial sodium influx rate was dependent on external sodium concentration in a manner well described by the Kirschner (1955) equation with Ks=0.02mEq/L and Mimax=61.68 μEq/100 g/hr. 4. Branchial sodium efflux rate was also dependent on external sodium levels in a manner loosely paralleling that of influx rate and suggestive of an exchange diffusion mechanism.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology
- Behavioral Neuroscience