Effect of saline acclimation on body water and sodium compartmentalization in Pekin ducks (Anas platyrhynchos)

The compartmentalization of body fluids was measured in individual Pekin ducks ( Anas platyrhynchos) drinking freshwater and after sequential acclimation to 300 mM NaCl and 400 mM NaCl. Total body water, extracellular fluid volume, plasma volume and exchangeable sodium pool were measured using (3)H(2)O, [(14)C]-polyethylene glycol, Evans Blue dye, and (22)Na dilution, respectively. Following acclimation to 300 mM NaCl, body mass decreased, but total body water and total exchangeable sodium pool were unaltered. Na and water were redistributed from the extracellular fluid (interstitial fluid) compartment into the intracellular fluid compartment. Following further acclimation to 400 mM NaCl, body mass, total body water and intracellular fluid volume decreased, but exchangeable sodium pool and extracellular fluid volume were unchanged. Our results suggested that, when Pekin ducks drink high but tolerable salinities, they maintain total body water, but redistribute Na(+) and water from interstitial fluid to the intracellular fluid compartment. When stressed beyond their ability to maintain total body water, they lose water from the intracellular fluid.