Functional aspects of the vestibular dark cells in the guinea pig: morphological investigation using ruthenium red staining technique.

The functional significance of the vestibular dark cells in the guinea pig was investigated using ruthenium red staining technique. The apical cell surface of the dark cell was covered by the fuzzy layer of the glycocalyx, which could be responsible for water and ion transport across the apical plasma membrane. It has been suggested that the otoconia have been at first demineralized by an unknown mechanism when they are attached to the dark cell surface, and the mucopolysaccharide and mucoproteins in the otoconial matrix are then absorbed by active pinocytosis in the dark cells. These functions may be closely related to the possible regulation of the calcium ion in the vestibular endolymph.