The Effect of Arterial Hypotension upon the Lactate, Pyruvate and Bicarbonate Concentrations of Brain Tissue and Cisternal CSF, and upon the Tissue Concentrations of Phosphocreatine and Adenine Nucleotides in Anesthetized Rats

Abstract

Abstract K aasik , A. E., L. N ilsson and B. K. S iesjö . The effect of arterial hypotension upon the lactate, pyruvate and bicarbonate concentrations of brain tissue and cisternal CSF, and upon the tissue concentrations of phosphocreatine and adenine nucleotides in anesthetized rats . Acta physiol. scand. 1970. 78 . 448–458. The effect of stagnant hypoxia upon the lactate, pyruvate and bicarbonate concentrations of brain tissue and cisternal CSF, and upon the tissue concentrations of phosphocreatine, ATP, ADP, and AMP was studied in anesthetized and curarized rats. The stagnant hypoxia was induced by arterial bleeding to a mean arterial blood pressure of 25–35 mm Hg. The hypotension was found to lead to moderate decreases in the phosphocreatine and ATP concentrations and to increases in the AMP and lactate concentrations. Restitution of a normal arterial blood pressure was found to give a rapid restitution of the ATP and AMP concentrations, to a slower restitution of the phosphocreatine concentration, and to a very slow disappearance of the lactate and pyruvate accumulated in the tissue and in the CSF. However, the cytoplasmatic NADH/ NAD + ratio, calculated from the intracellular lactate and pyruvate concentrations, and from the pHi' values, was found to normalize already 2 min after the reinfusion of the blood. There was a linear relationship between the lactate accumulated in the intracellular space, and the pHi', and the slope of the line (Δ lactate/Δ pH) indicated that the intracellular buffer capacity, thus calculated, is lower than that of whole blood in vitro .