The Effect of Acute and Chronic Hypercapnia upon the Lactate, Pyruvate, α‐ketoglutarate, Glutamate and Phosphocreatine Contents of the Rat Brain

Abstract

The influence of hypercapnia upon the tissue contents of lactate, pyruvate, α‐ketoglutarate, glutamate and phosphocreatine was studied in rats exposed to about 11 % CO₂ for 15 and 45 min, and for 3, 24, 48 and 72 h, respectively. Acute hypercapnia (15 and 45 min) was associated with highly significant decreases in the lactate, pyruvate, α‐ketoglutarate, glutamate and phosphocreatine contents. In sustained hypercapnia (3 h and onwards), the lactate, pyruvate and α‐ketoglutarate contents were partially restored but phosphocreatine and glutamate remained decreased. In acute hypercapnia the intracellular lactate/pyruvate ratio was increased, but it returned to normal in sustained hypercapnia (> 24 h). The results suggest that the intracellular lactate/pyruvate ratio is affected both by changes in the intracellular pH and by changes in the NADH/NAD⁺ ratio.