AJP - Regulatory, Integrative and Comparative Physiology, Vol 239, Issue 1 180-R183, Copyright © 1980 by American Physiological Society
Extracellular hyperosmolality and body temperature during physical exercise in dogs
S. Kozlowski, J. E. Greenleaf, E. Turlejska and K. Nazar
The purpose of this study was to test the hypothesis that thermoregulation
during exercise can be affected by extracellular fluid hyperosmolality
[Osm] without changing the plasma Na+ concentration. The effects of
preexercise venous infusions of hypertonic mannitol and NaCl solutions on
rectal temperature (Tre) responses were compared in dogs running at
moderate intensity for 60 min on a treadmill. Plasma E1Na+] was increased
by 12 meq/l (P less than 0.05) after NaCl infusion, and decreased by 9
meq/l (P less than 0.05) after mannitol infusion. Both infusions increased
plasma [Osm] by 15 mosmol/kg (P less than 0.05). After both infusions, Tre
was essentially constant during 60 min rest. However, compared with the
noninfusion exercise increase in Tre of 1.3 degrees C, Tre increased by 1.9
degrees C (delta delta Tre = 0.5 degrees C, P less than 0.05) after both
postinfusion exercise experiments. It was concluded that inducing
extracellular hyperosmolality, without elevating plasma [Na+], can induce
excessive increases in Tre during exercise but not at rest.
