Effects of Oxygen Saturation and Pco ₂ on Brain Uptake of Glucose Analogues in Rabbits

Abstract

Abstract:Effects of Oxygen Saturation and Pco, on Brain Uptake of Glucose Analogues in Rabbits• The effect of oxygen saturation and Pco, on brain uptake of glucose analogues was studied in rabbits. Using a modified Oldendorf technique, l4 C-labeled glucose analogues with a 3 H 2 O reference standard were introduced into the cerebral circulation via the common carotid artery, and the radioactivity of the ipsilateral cerebral cortex was counted and expressed in terms of a brain uptake index (BUI).Severe hypoxia (oxygen saturation < 18%) resulted in approximately a 40% decrease in the BUI of 2-deoxy-D-glucose and a 45% decrease in the BUI of 3-0-methyl-D-glucose. Severe hypercapnia (Pco, = 100 mm Hg) caused a 45% decrease in the BUI of both of these glucose analogues. Hypercapnia superimposed on severe hypoxia had no additional effect. Hypocapnia (Pco, = 15 mm Hg) increased the BUI of 3-0-methyl-D-glucose by 35% of the control value, and this increase was extremely sensitive to competitive inhibition. When BUI values were plotted against pH rather than Pco, for the same experiments, there was a good correlation with the calculated linear regression.These results are compared with previous findings on pathologically induced changes in brain uptake of glucose analogues, and the possible role of blood flow is considered in detail. Additional Key Wordshypoxia hypercapnia hypocapnia hyperoxia glucose analogue transport across blood-brain barrier

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“…Finally, alkalemia and hypocapnia increase neuronal excitability (32), reduce the epileptic threshold and/or prolong convulsive activities (33). In animal studies, hypocapnia led to an increased cerebral consumption and depletion of local glucose (34,35). Hypocapnia has also been associated with neurotoxicity (12), by inducing the release of cytotoxic excitatory amino-acid (36), increasing dopamine levels in the basal ganglia (37) and by promoting the inappropriate incorporation of choline into the phospholipids of cell membranes (38).…”