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TRANSPORT OF SUGARS INTO MICROVESSELS ISOLATED FROM RAT BRAIN: A MODEL FOR THE BLOOD‐BRAIN BARRIER 1
Author(s) -
Kolber Alan R.,
Bagnell C. Robert,
Krigman Martin R.,
Hayward Jean,
Morell Pierre
Publication year - 1979
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1979.tb05171.x
Subject(s) - microvessel , horseradish peroxidase , kinetics , chemistry , biophysics , membrane , glucose transporter , blood–brain barrier , passive transport , facilitated diffusion , mannitol , transmission electron microscopy , glucose uptake , fructose , electron microscope , biochemistry , enzyme , insulin , biology , central nervous system , angiogenesis , optics , cancer research , quantum mechanics , neuroscience , chemical engineering , engineering , endocrinology , physics
— Microvessels (primarily capillaries) were isolated from the brains of rats 25‐35 days of age. This preparation was characterized by light, transmission, and scanning electron microscopy. Transmission electron microscopy revealed that the endothelial cell membranes were intact and were impermeable to horseradish peroxidase. However, scanning electron microscopy revealed that damage to the membrane occurred during isolation. The isolated microvessel preparations were metabolically competent as demonstrated by their ability to metabolize [ 14 C]glucose. Aliquots of microvessel preparation were incubated with radioactive non‐metabolizable analogs of D‐glucose at various concentrations. The kinetics of accumulation of radioactivity in the capillaries were analyzed according to a model for carrier‐mediated diffusion and affinity constants for 3‐ O ‐methyl‐ D‐glucose and 2‐deoxyglucose were calculated (about 18 mM at 20°C in each case). These affinity constants are somewhat greater than that expected from whole animal experiments reported by other laboratories. This discrepancy is probably accounted for by the presence of a passive diffusion component. However, despite this complication, the primary mechanism for entry of D‐glucose analogues at physiological concentrations is compatible with carrier‐mediated transport since: the uptake of sugar analogs was shown to be saturable, to exhibit competition for uptake between structurally similar molecules, and to be non‐concentrative. In contrast, the uptake of glycerol, mannitol, and L‐glucose by isolated microvessels obeyed the kinetics of simple passive diffusion and was not saturable. Our results are compatible with the concept that the capillary is the anatomic locus of the blood‐brain barrier and that this structure contains the carrier‐mediated transport system for monosaccharide penetration into brain.