The characteristics of glucose transport across the blood brain barrier and its relation to cerebral glucose metabolism.

The evidence suggests that glucose transport across the blood brain barrier (BBB) in the dog is normally not a rate-limiting step in cerebral metabolism; however, transport may become rate-limiting under conditions of extreme hypoglycemia or anoxia. Studies on the mechanism of glucose transport from blood to brain do not at this time permit us to distinguish between active transport and facilitated diffusion; however, a decrease in the rate of unidirectional transport during anoxia suggests that an energy-dependent process may be involved. In spite of this evidence, glucose transport across the BBB is similar to the facilitated diffusion of glucose into the red cell in terms of the structural requirements of the glucose molecule, the pattern of inhibition by phlorizin, phloretin and cytochalasin B, and the lack of sensitivity to Na+ or insulin.