Concentration of hypoxanthine in both cerebrospinal fluid and brain tissue increases under intensive hypoxia only

The relationships between the concentrations of glycogen, glucose, lactate, adenosine triphosphate (ATP) and hypoxanthine in the brain tissue, and the hypoxanthine and lactate concentration in cerebrospinal fluid and blood were examined after exposure of rats to hypoxia. The animals (1 and 10 days old) were exposed to hypobaric hypoxia for 1-12 h, pO2 11.3 kPa (mild), pO2 8.6 kPa (moderate), pO2 6.4 (strong) and pO2 4.7 kPa (severe) in inspired air. The concentration of hypoxanthine in both cerebrospinal fluid and brain tissue increases in severe hypoxia. This severe hypoxia was related to a decrease of ATP level in brain tissue. This study showed that the level of hypoxanthine in blood did not closely correlate to the level of hypoxanthine in brain tissue and cerebrospinal fluid. Extremely high hypoxanthine values in the blood might indicate a decrease in ATP content in brain tissue.