Metabolic disorder of otoconia after streptomycin intoxication.

Little is known about the origin or the metabolism of otoconia. Streptomycin sulfate was found to cause a decrease in their number on the otolithic membrane of the utricle and saccule in guinea pigs. The remaining otoconia on the otolithic membrane varied in shape and size and giant otoconia with multilayered arrangement were observed by means of a scanning electron microscope. These otoconia contained the normal amount of calcium in the form of standard calcium calcite crystal. The lost otoconia were found attached to the surface of some vestibular dark cells. Otoconia in this new position were irregular, shrunken or fragmented. Their calcium content, measured with an X-ray micro-analyzer, was variably diminished. The dark cells appeared to be actively engaged in absorption of calcium ions, from the attached otoconia. The dark cell is considered to be a receptacle for the disposal of otoconia.