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.