Intracellular pH in unanesthetized dogs during panting.

Intracellular pH, arterial blood gases and several plasma enzymes were estimated in unanesthetized dogs during a 3-hour exposure to 30 degrees C/50% relative humidity, and 40 degrees C/50% relative humidity. No change occurred during mild heat stress, whereas during severe heat stress a profound respiratory alkalosis developed together with an increase in intracellular pH from 7.03 to 7.29. Most plasma enzymes increased by about 300% or more. In spite of extreme panting body temperature rose to 42.2 degrees C. Exposure to 40 degrees C/50% relative humidity with 4% CO2 in the climatic chamber inhibited the respiratory alkalosis and the increase of plasma enzymes. Though the panting frequency was lower the ventilatory heat dissipation was more efficient. Body temperature rose to only 39.8 degrees C. It is concluded that the intracellular buffering is not able to prevent marked changes of the intracellular pH during panting.