Cytochrome oxidase and hexokinase activities in an infusion edema model with preserved blood flow

Despite numerous investigations, the mechanisms underlying the neurological deficits observed in association with interstitial edema remain unclear. A recent study has demonstrated that the cerebral blood flow (CBF) in edematous white matter is unchanged if the blood flow values are corrected for dilution. In contrast, the cerebral glucose metabolism (CMRgl) has been found to be increased. In order to examine the effects of interstitial edema on the oxidative metabolism, we measured the cytochrome oxidase (CYO) activity, a marker of mitochondrial respiration, and the hexokinase (HK) activity, a marker of glycolysis, together with CBF and CMRgl employing the iodoantipyrine and deoxyglucose autoradiography in an infusion edema model in rats. In agreement with the previous study, CBF was not significantly changed in the edematous hemisphere. No significant alterations in CMRgl and HK activity were noted. In contrast, there was a significant decrease in CYO activity in the edematous hemisphere (-17%; p < 0.01), which was correlated to the edema. These findings suggest that interstitial edema causes a decreased mitochondrial respiratory function despite a maintained circulation. This may be explained by postulating a decreased oxygen delivery and/or accumulation of lactate, both of which have been shown to interfere with mitochondrial respiratory function.