Calcium mobilization in isolated epithelial cells of the endolymphatic sac.

Endolymphatic sac epithelial cells were isolated from the endolymphatic sac of the guinea pig by enzymatic and mechanical dissociation. The intracellular free calcium ion concentrations ([Ca2+]i) of the isolated cells were determined using the Ca(2+)-sensitive dye fura-2. The isolated cells were classified into two types, i.e. light and dark cells. In the resting state, [Ca2+]i in the cells was variable in both types of cells. In the presence of 200 microM ATP, there was a rapid rise in [Ca2+]i. These findings suggest that endolymphatic sac epithelial cells may have receptor-mediated Ca channels which may play an important role for a nerve-mediated local feedback system of the endolymphatic sac to regulate homeostasis of endolymph volume, pressure and electrolyte balance.

Isolated vestibular sensory cells in the guinea pig.

Vestibular sensory cells were isolated from the utricular macula or cristae ampullares of the guinea pig by enzymatic and mechanical dissociation. The isolated cells were classified into three types: flask-shaped type I sensory cells, rod-shaped type II sensory cells and round-shaped supporting cells. The cilia of type I sensory cells in the crista ampullaris were longer than those in the corresponding cell type in the utricular macula, while no morphological differences of the cell bodies were noted between crista ampullaris and utricular macula. Isolated living vestibular cells have a motile capacity. After exposure to a hypo-osmotic medium, the type I sensory cells showed tilting of the hair bundle. This change in shape may be closely related to the active mechanical transduction control.

Motile responses of isolated vestibular hair cells.

Vestibular sensory cells were isolated from the utricular macula or crista ampullaris of the guinea pig by enzymatic and mechanical dissociation. Isolated vestibular hair cells, especially type I hair cells, showed an active motile capacity. After exposure to a medium containing high concentration of potassium, or to a hypoosmotic medium, the type I hair cells showed tilting of their hair bundle to about 15 degrees. Given the tight and dense structure of the vestibular epithelium, the changes in shape of the isolated vestibular hair cells may in vivo lead to an influence of the mechano-sensitive stereocilia and modulate stiffness and compliance of the receptor structure as a whole including its cupular or macular relationship. This active mechanical events could be closely related to an active adaptation process.