Stimulation of glucose analogue uptake by cerebral microvessel endothelial cells by a product released by astrocytes.

Astroglial cells, both normal and neoplastic, secreted a product that stimulated glucose uptake by cerebral microvessel endothelial cells by 23% and 50%, respectively. Neither cerebral microvessel smooth muscle cells nor oligodendrocytes affected endothelial cell glucose uptake. The astrocytic product(s) did not affect glucose uptake by aortic endothelial cells. The effect on the cerebral microvessel endothelial cells increased with increasing time of exposure of the cells to the astroglial product(s), and required the constant presence of the astrocytic product to be maintained. The presence of a protein synthesis inhibitor during endothelial cell exposure to the astroglial conditioned medium blocked the stimulation of glucose uptake. Treatment of the astrocytic product with a protease destroyed its effectiveness. These results support the hypothesis that astrocytes induce the expression of at least one blood-brain barrier property by the cerebral microvasculature, and suggest that this induction may be produced by a protein released by the astrocytes.