Regional cerebral glucose utilization transiently increases during mild hypoxia.
Regional cerebral glucose utilization (rCMRglu) was studied during mild hypoxic hypoxia in awake free-ranging rats. Rats were prepared with chronic arterial and venous catheters and placed in individual chambers for 4 days to recover from surgery before the experiments. The catheters were accessible by passing them through the top of the chambers. Hypoxia was induced by filling the chambers with a gas mixture consisting of 11% O2 in a balance of N2. Regional CMRglu and physiological parameters were measured in normoxic controls and in rats that had been hypoxic for 2 and 17 min before beginning the measurements. Regional CMRglu was measured in 17 brain regions using [6-14C]glucose. PaO2 decreased from 88 mm Hg in the controls to approximately 40 mm Hg during hypoxia. In the early stages of hypoxia (2-12 min), rCMRglu increased approximately 10-25% above the control rates. In later stages of hypoxia (17-27 min), rCMRglu was not different from that in the normoxic controls. The increase in rCMRglu in the early hypoxia was not blocked by propranolol (1.4 mg/kg), indicating that beta-adrenergic receptors were not involved with the increase in rCMRglu. It was concluded that mild hypoxia is associated with an increased rate of cerebral glucose utilization; however, the increase is transitory, with glucose utilization returning to control rates before 17 min.
MacNeill
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Department of Surgery (Neurosurgery), Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
Bryan
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RM
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001921:Brain / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D000860:Hypoxia / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D012016:Reference Values; D013997:Time Factors; D014018:Tissue Distribution
D001786:Blood Glucose; D005947:Glucose