[Motility and cytoskeleton of isolated vestibular hair cells of the guinea pig].

Vestibular hair cells were isolated from the vestibular endorgan of the guinea pig by enzymatic and mechanical dissociation. The isolated cells were divided into three types: flask-shaped type I cells, rod-shaped type II cells and round supporting cells. The cilia of type I cells in the crista were longer than those in the corresponding cell type in the macula. After exposure to a medium containing a high concentration of potassium, to a hypoosmotic (280mOsm) medium or to medium containing ATP, the type I cells showed tilting of the neck portion accompanied by tilting of the hair bundle. Isolated living type I vestibular cells are capable of self-movement. Actin and the other proteins associated with the cytoskeleton are thought to be related to vestibular hair cell motility. The location of F-actin in the isolated vestibular hair cell was studied by using FITC-labeled phalloidin. In hair cells fixed by paraformaldehyde, actin filaments found to be located in the hair bundle and cuticular plate. In frozen-fixed cells perfused by artificial perilymph, the filaments were heavily located in the hair bundle and cuticular plate as well as throughout the cytoplasm. In frozen-fixed cells perfused with artificial endolymph containing a high concentration of potassium, staining of the hair bundle and cuticular plate was weaker. These changes in the actin staining pattern may be closely related to the mechanism of self-movement. Given the tight and dense structure of the vestibular epithelium, the shape changes of the isolated vestibular hair cells may in vivo lead to modulate stiffness of the apical portion of type I cells, and compliance of the receptor structure as a whole including its cupular or macular relationship. These active mechanical events could be closely related to an active adaptation process.