Three-dimensional and ultrastructural relationships between intermediate cells and capillaries in the gerbil stria vascularis

Structural relationships between intermediate cells and capillaries in the stria vascularis of gerbils were examined by confocal laser microscopy and electron microscopy. Immunostaining for an inward rectifier K⁺ channel (Kir4.1), which was localized to intermediate cells, was used to determine the three-dimensional distribution of intermediate cells. These cells constituted a honeycomb-like network, and their dendritic processes surrounded not only capillaries but also the basolateral surface of epithelial marginal cells. On the basis of the above finding and the large K⁺ conductance in intermediate cells, we propose that the network composed of intermediate cells has a spatial K⁺ buffering function. Transmission electron microscopy revealed the absence of the basal lamina in some regions and the presence of a gap junction-like membrane association between intermediate cells and pericytes and/or endothelial cells. This result supported our previous finding that intermediate cells were dye-coupled with pericytes and endothelial cells. The presence of gap junctions between intermediate cells and pericytes and/or endothelial cells suggests that endothelial cells and pericytes may play roles other than forming a structural route for blood circulation.