Ion-osmotic hyperthermia during exercise in dogs

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Thermoregulation

Background:

• Understanding factors influencing body temperature during exercise is crucial for preventing heat-related illnesses.
• Plasma sodium and osmotic concentrations are potential regulators of thermoregulation during physical exertion.

Purpose of the Study:

• To investigate the impact of intravenous NaCl solutions on rectal temperature (Tre) regulation in dogs during rest and exercise.
• To determine the relationship between plasma electrolyte/osmotic concentrations and exercise-induced hyperthermia.

Main Methods:

• Dogs were infused with varying concentrations of NaCl solutions before and during treadmill exercise.
• Rectal temperature, plasma sodium ([Na+]), and osmotic concentrations were monitored.
• Plasma volume changes and water consumption effects were also assessed.

Main Results:

• Hypertonic NaCl infusions elevated plasma [Na+] and osmolality, leading to higher Tre during exercise but not at rest.
• No further Tre increase was observed above 170 meq/liter [Na+] or 325 mosmol/kg osmolality.
• Water consumption during exercise normalized Tre, [Na+], and osmolality.
• Plasma volume changes did not affect Tre dynamics during exercise.

Conclusions:

• Exercise Tre responses in dogs mirror human responses to elevated plasma [Na+] and osmolality.
• Plasma volume changes do not significantly influence exercise-induced thermoregulation.
• Water intake mitigates ion-osmotic hyperthermia during exercise.