Cerebral Glucose and Energy Utilization during the Evolution of Hypoxic—Ischemic Brain Damage in the Immature Rat

Abstract

The cerebral metabolic rate for glucose (CMRg1) and cerebral energy utilization (CEU) were assessed in immature rats during recovery from cerebral hypoxia-ischemia. CMRg1 was determined using a modification of the Sokoloff technique with 2-deoxy-[14C]glucose (2-DG) as the radioactive tracer. CEU was determined using the Lowry decapitation technique. Seven-day postnatal rats underwent unilateral common carotid artery ligation, followed 4 h thereafter by exposure to 8% oxygen at 37 degrees C for 3 h. At 1, 4, or 24 h of recovery, the rat pups underwent those procedures necessary for the measurement of either CMRg1 or CEU. At 1 h of recovery, the CMRg1 of the cerebral hemisphere ipsilateral to the carotid artery occlusion was 97% of the control rate (8.7 mumol 100 g-1 min-1) but was only 48% of the control in the contralateral hemisphere. At 4 h of recovery, the CMRg1 was increased 49% above baseline in the ipsilateral hemisphere, decreasing thereafter to 84% of the control at 24 h. The CMRg1 of the contralateral hemisphere normalized by 4 h of recovery. An inverse correlation between endogenous concentrations of ATP or phosphocreatine and CMRg1 in the ipsilateral hemisphere was apparent at 4 h of recovery. CEU in the ipsilateral cerebral hemisphere was 64 and 46% of the control (3.47 mmol approximately P/kg/min) at 1 and 24 h, respectively (p < 0.05) and 77% of the control at 4 h of recovery. CEU in the contralateral hemisphere was unchanged from the control at all measured intervals. Correlation of the alterations in CMRg1 with those in CEU at the same intervals indicated that substrate supply exceeds energy utilization during early recovery from hypoxia-ischemia. The discrepancy combined with a persistent disruption of the cerebral energy state implies the existence of an uncoupling of mitochondrial oxidative phosphorylation as one mechanism for the occurrence of perinatal hypoxic-ischemic brain damage.