title: Ion-osmotic hyperthermia during exercise in dogs.
abstract: 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: D000818:Animals; D001798:Blood Proteins; D001833:Body Temperature Regulation / Q000187:drug effects*; D004285:Dogs; D004326:Drinking; D006400:Hematocrit; D008297:Male; D009994:Osmolar Concentration; D005082:Physical Exertion; D010953:Plasma Volume; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D001798:Blood Proteins; D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium