Acid-base changes in brain and skeletal muscle of maturing rats

¹ Department of Pharmacology, University of Utah College of Medicine, Salt Lake City, Utah

Tissue acid-base changes during maturation were studied by making complete acid-base comparisons among 8-day-old, 25-day-old, and adult rats. Micromethods were used to obtain individual values for blood pH and for CO₂ content of plasma, brain, and skeletal muscle. The results showed that the CO₂ content of both brain and muscle are high in 8-day-old animals but decrease to adult levels in the 25-day-old rat. Plasma total CO₂ does not change during maturation. Fractionation of muscle total CO₂ into extra- and intracellular components indicated that muscle cell pH is elevated in 8-day-old animals because intracellular bicarbonate levels are markedly greater than those observed in older animals. It was concluded that changes in tissue CO₂ content during growth are due to a marked decrease in intracellular bicarbonate concentrations. Although the partition of brain total CO₂ was not feasible due to uncertainties in extracellular space measurements, the results indicated that during maturation brain cell acid-base parameters undergo changes similar to those observed in skeletal muscle.

Key Words: Brain acid-base changes during maturation • muscle acid-base changes during maturation • maturation • brain CO₂ muscle CO₂ • immature brain and muscle CO₂ • intracellular pH during development

Submitted on March 11, 1963