Intracellular changes in the endolymphatic sac after labyrinthectomy.

Intracellular changes within the lining epithelium of the murine endolymphatic sac were investigated following surgical labyrinthectomy. The light and the dark epithelial cells reacted differently. Some light cells showed altered morphology after labyrinthectomy. The smooth endoplasmic reticulum formed a tubular network in the apical cytoplasm which was contiguous with the extremely well developed rough endoplasmic reticulum. These light cells also contained numerous granules. Such cell modifications indicated a secretory potential in this type of light cells. The dark cells showed signs of increased activity, with an augmentation of endoplasmic reticulum and an increased electron density of the cytoplasm. The dark cells increased their luminal surface to such an extent that they frequently covered the luminal surface of neighbouring light cells. Our hypothesis is that the dark cells may, in some way, control the function of the light cells and in this way also the absorptive mechanisms of the endolymphatic sac.