Intracellular pH of the Brain in Arterial Hypoxemia, Evaluated with the CO₂Method and from the Creatine Phosphokinase Equilibrium

Abstract

The fall in intracellular pH in the brain due to lactacidosis was evaluated with the CO₂method, and from the creatine phosphokinase equilibrium, in rats exposed to a lowering of the arterial Po₂to 40, 30, and 20 mm Hg, respectively. The CO₂method gave consistently lower pH values than the CPK method in the hypoxemic groups. Calculations of the intracellular pH from the Poo₂and the measured buffer base changes indicated that the CO₂method gives systematic errors at the low CO₂contents encountered and with the short hypoxemic periods used. A correlation between increase in intracellular lactate and decrease in intracellular pH showed that when the intracellular lactate concentration increases by 5, 10, and 15 mEqv/kg at constant CO₂tension, the intracellular pH decreases by 0.10, 0.21, and 0.32 units, respectively.

Key Words:

• Brain
• CPK equilibrium
• hypoxemia
• intracellular pH