[The mechanism of formation of the otoconia in the utricular supporting cells of the guinea pig].

The mechanism of formation of the otocania in the utricular supporting cells of the guinea pig was investigated by means of an organ culture system using the potassium pyroantimonate (PA) precipitation method. The utricular otoconia and the secretory granules and mitochondria in the utricular supporting cells immediately after removal from the animal were positive to PA. When the specimens were treated with ethylene-glycol-0, 0-bis (2-aminoethyl)-N, N, N', N'-tetraacetic acid (EGTA) as a chelater prior to the PA staining, almost all deposits disappeared. This indicates that calcium is the main ion precipitated by the PA method. The utricules of the guinea pig were exposed to 30 mg of streptomycin sulfate per ml for 3 days in culture. The number of large lysosomes which contained vesicles and myeloid bodies in the supporting cells increased. On the other hand, the secretory granules were reduced in the cytoplasm of the supporting cells. Acid phosphatase activity in the lysosomes and the Golgi apparatus decreased. As a result of the PA treatment, these large lysosomes, especially the vesicles which were in them, contained a large quantity of calcium ion. From these findings, I conclude that the mechanism of formation of otoconia is as follows: The area of formation of otoconia is the supporting cells. Globular substances are the precursors of otoconia, and they contain calcium ion which was taken into the supporting cells. These globular substances are made in close relationship among the endplasmic reticula, secretory granules and lysosomes. They are secreted from the supporting cells and form the mature otoconia on the otoconial membrane.