HYPOXIA INCREASES GLUCOSE-TRANSPORT AT BLOOD-BRAIN-BARRIER IN RATS

Prolonged hypoxia causes several adaptive changes in systemic physiolo gy and tissue metabolism. We studied the effects of hypobaric hypoxia on glucose transport at the blood-brain barrier (BBB) in the rat. We f ound that hypoxia increased the density of brain microvessels seen on immunocytochemical stains using an antibody to the glucose transportin g protein GLUT. In addition, we found that hypoxia increased the densi ty of GLUT in isolated cerebral microvessels as determined by specific cytochalasin B binding. The higher GLUT density in isolated cerebral microvessels was evident after 1 wk of hypoxia and was associated with decreased activity of gamma-glutamyl-transpeptidase. Consistent with these findings, we also demonstrated that 3 wk of hypobaric hypoxia ca used increased unidirectional transport of glucose at the BBB in sever al brain regions in vivo, as determined by the doubly labeled single-p ass indicator-fractionation atrial bolus injection method in anestheti zed rats. We conclude that chronic hypobaric hypoxia is associated wit h increased glucose transport at the BBB.