EFFECT OF MARKED HYPERVENTILATION UPON TISSUE LEVELS OF NADH, LACTATE, PYRUVATE, PHOSPHOCREATINE, AND ADENOSINE PHOSPHATES OF RAT BRAIN

In order to study the effect of pronounced hyperventilation upon the redox state of brain tissue rats were hyperventilated with air and measurements were made of the cortical level of NADH, using the microfluorometric method of Chance. Control measurements were made of the tissue concentrations of lactate, pyruvate, ATP, ADP, AMP, and phosphocreatine during and after the hyperventilation. It was found that when the rats were hyperventilated to arterial pCO2 levels below about 20 mm Hg, the NADH fluorescence invariably increased. Although part of this increase may represent a hemodynamic artefact due to a decrease in the tissue blood volume, a large part of it should represent a true reduction in the NADH/NAD+ system. With hyperventilations of this degree there was a proportionally larger increase in lactate than in pyruvate and thus an increased lactate/pyruvate ratio, but there were no changes in phosphocreatine, or in adenosine phosphates, except for a small but significant increase in the AMP concentration. The NADH increase during hyperventilation was slightly decreased when pure oxygen was administered and completely normalized when 3–5 % CO2 was given. The experiments thus strongly suggest an increased reduction in the NADH/NAD+ system of the brain during pronounced hyperventilation. © 1969 Scandinavian Physiological Society