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The complementary membranes forming the blood-brain barrier
Richard A Hawkins1, Darryl R Peterson, Juan R Viña
1Department of Physiology and Biophysics, Finch University of Health Science/The Chicago Medical School, North Chicago, Illinois 60064-3095, USA. HawkinsR@finchcms.edu
IUBMB Life
|December 20, 2002
Summary
The blood-brain barrier actively regulates brain fluid by controlling amino acid and glucose transport. Specialized transporters in luminal and abluminal membranes ensure precise nutrient and waste movement, maintaining brain homeostasis.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Brain capillary endothelial cells form the blood-brain barrier (BBB).
- The BBB exhibits polarized plasma membrane domains (luminal and abluminal).
- Polarized transporter distribution is crucial for regulating brain extracellular fluid.
Purpose of the Study:
- To investigate the polar arrangement of amino acid and glucose transporters in the BBB.
- To understand how transporter organization contributes to brain fluid regulation.
- To explore the role of the gamma-glutamyl cycle in modulating amino acid transport.
Main Methods:
- Experiments on isolated membrane vesicles from bovine brain capillary endothelial cells.
- Demonstration of polar transporter arrangements.
- Immunoblotting studies to identify glucose transporter types.
Main Results:
- Passive amino acid carriers are luminal; Na-dependent transporters are abluminal.
- The gamma-glutamyl cycle and abluminal transporters modulate amino acid influx.
- Passive glucose transporters exist in both domains; a high-affinity Na-dependent carrier is abluminal.
- Evidence for multiple, asymmetrically distributed passive glucose transporters.
Conclusions:
- The BBB actively regulates brain extracellular fluid.
- Distinct functions of luminal and abluminal membrane domains are critical for BBB regulatory roles.
- Transporter localization dictates directional movement of substances across the BBB.