Ion-osmotic hyperthermia during exercise in dogs

Am J Physiol. 1976 Jan;230(1):74-9. doi: 10.1152/ajplegacy.1976.230.1.74.


The influence of intravenous infusions of various concentrations of NaCl solutions on temperature regulation was investigated in dogs at rest and during moderate exercise for 1 h on a treadmill. Infusion of hypertonic solutions either before and during exercise resulted in elevated (P less than 0.05) plasma Na+ and osmotic concentrations and produced higher equilibrium levels (P less than 0.05) of rectal temperature (Tre) during exercise (prehypertonic 40.9 degrees C vs. no infusion 40.4 degrees C; hypertonic 40.8 degrees C vs. isotonic infusion 40.4 degrees C), but not at rest. Increasing the [Na+] and osmotic concentrations above 170 meq/liter and 325 mosmol/kg, respectively, resulted in no additional increase in exercise Tre. Water consumption during exercise decreased (P less than 0.05) plasma [Na+], osmolality, and the equilibrium level of Tre to control levels. There was no effect of changes in plasma volume (PV) of +/- 8% on the time course, equilibrium level, or change in Tre during exercise. At the end of exercise, there were moderate correlations (P less than 0.01) between Tre and [Na+] (r = 0.51) and Tre and osmoti (r = 0.52) concentrations. It was concluded that a) the exercise Tre responses of the dog respond quantitatively like man to elevated plasma [Na+] and osmolality, b) the Tre levels are not influenced by changes in PV, and c) water intake significantly reduces the ion-osmotic hyperthermia.

MeSH terms

  • Animals
  • Blood Proteins
  • Body Temperature Regulation / drug effects*
  • Dogs
  • Drinking
  • Hematocrit
  • Male
  • Osmolar Concentration
  • Physical Exertion*
  • Plasma Volume
  • Potassium / blood
  • Sodium / blood
  • Sodium Chloride / pharmacology*


  • Blood Proteins
  • Sodium Chloride
  • Sodium
  • Potassium