Effect of labyrinthectomy on the endolymphatic sac. A histological, ultrastructural and computer-aided morphometric investigation in the mouse.

A time sequence study of the effect of hemilabyrinthectomy on the endolymphatic sac was performed in mice. Light and transmission electron microscopy of the sac showed significant morphological changes of the epithelial lining and adjacent structures. Initially (2 and 4 days post-labyrinthectomy) the sac lumen was collapsed, but later (7 days post-labyrinthectomy) it was dilated or 'ballooned' and filled with a darkly staining homogeneous substance. This substance, which has been identified histochemically as a proteoglycan, appeared to be secreted from the epithelium of the endolymphatic sac. This finding suggests that the endolymphatic sac may be capable both of absorbing and of secreting endolymph.