Glucose transport by isolated plasma membranes of the bovine blood-brain barrier
Lee, W.J.; Peterson, D.R.; Sukowski, E.J.; Hawkins, R.A.
American Journal of Physiology 272(5 Pt 1): C1552-C1557
1997
ISSN/ISBN: 0002-9513 PMID: 9176146 Document Number: 483395
Luminal and abluminal endothelial plasma membrane vesicles were isolated from bovine cerebral microvessels, the site of the blood-brain barrier. Glucose transport across each membrane was measured using a rapid-filtration technique. Glucose transport into luminal vesicles occurred by a stereospecific energy-independent transporter (Michaelis-Menten constant (K-m) = 10.3 +- 2.8 (SE) mM and maximal velocity (V-max) = 8.6 +- 2.0 nmol cntdot mg protein-1 cntdot min-1). Kinetic analysis of abluminal vesicles also showed a transport system with characteristics similar to the luminal transporter (K-m = 12.5 +- 2.3 mM and V-max = 10.0 +- 1.0 nmol cntdot mg protein-1-min-1). These functional, facilitative glucose transporters were symmetrically distributed between the luminal and abluminal membrane domains, providing a mechanism for glucose movement between blood and brain. The studies also revealed a Nadependent transporter on the abluminal membrane with a higher affinity and lower capacity than the facilitative transPorters (Km = 130 +- 20 mu-M and V-max = 1.59 +- 0.44 nmol cntdot mg protein-1 cntdot min-1). The abluminal Na-dependent glucose transporter is in a position to transport glucose from the brain extracellular fluid into the endothelial cells of the blood-brain barrier. The functional significance of its presence there remains to be determined.