BACKGROUND:Human umbilical endothelial cells were used to model the vascular component of the blood-retinal barriers and to examine the capacity of glial cultures to modulate endothelial cell resistivity in vitro. METHODS:Endothelial cell resistivity was monitored with and without cocultured human retinal glia. Immunohistochemistry indicated that both macroglia and microglia were present in one culture, while only macroglia were detectable in the second culture. RESULTS:Both cocultures produced increased resistivity in the target endothelial cells; however, a further significant increase in resistivity was noted with the glial coculture containing microglia. The results suggest that the presence of microglia significantly increases the capacity of astrocytes and Müller cells to modulate endothelial cell resistivity.