Structural organization of the outer hair cell wall.

The lateral wall of the mammalian outer hair cell has specialized structures composed of "subplasma lamina" and "micropillars." These structures anchor the subsurface cisternae to the inner leaflet of the cell membrane. The micropillars are arranged in parallel arrays encircling the entire inner side of the outer hair cell. The subplasma lamina appears sheet-like with rows of indentations and ridges in parallel arrays or in grid patterns among the specimens prepared for scanning electron microscopy. It is interpreted that these indentations are formed by the loss of the micropillars due to the osmium digestion. It is suggested that the subplasma lamina and micropillars may provide a rigid structure of the cylindrical shape and also may be involved in the motile activity of the outer hair cell.