|dc.description.abstract||The primary objective of this investigation was that of providing a
comprehensive tissue-by-tissue assessment of water-electrolyte status in
thermally-acclimated rainbow trout, Salmo gairdneri. To this end levels
of water and the major ions, sodium, chloride and potassium were evaluated
in the plasma, at three skeletal muscle sites, and in cardiac muscle,
liver, spleen, gut and brain of animals acclimated to 2°, 10° and 18°C.
The occurrence of possible seasonal variations in water-electrolyte
balance was evaluated by sampling sununer and late fall-early winter
populations of trout.
On the basis of values for water and electrolyte content, estimates
of extracellular and cellular phase volumes, cellular electrolyte concentrations
and Nernst equilibrium potentials were made. Since accurate
assessment of the extracellular phase volume is critical in the estimation
of cellular electrolyte concentrations and parameters based on assumed
cellular ion levels, [14 C]-polyethylene glycol-4000, which is assumed to
be confined to the extracellular space, was employed to provide comparisons
with various ion-defined spaces (H20~~s, H20~~/K and H20~~s). Subsequently,
the ion-defined space yielding the most realistic estimate of extracellular
phase volume for each tissue was used in cellular electrolyte calculations.
Water and electrolyte content and distribution varied with temperature.
Tissues, such as liver, spleen and brain appeared to be the most thermosensitive,
whereas skeletal and cardiac muscle and gut tissue were less
influenced. 'Summer' series trout appeared to be more capable of
maintaining their water- electrolyte balance than the ~fall-winter' series
The data are discussed in terms of their possible effect on
maintenance of appropriate cellular metabolic and electrophysiological