The effect of gentamicin on the glycocalyx and the ciliary interconnections in vestibular sensory cells: a high resolution scanning electron microscopic investigation.

Changes in glycocalyx structure and ciliary interconnections of the vestibular sensory cells are demonstrated after gentamicin administration. A special high resolution scanning electron microscope and a tannic acid-osmium staining technique giving an almost three dimensional view were used to achieve this purpose. Guinea pigs were injected with a single dose of 5 mg of gentamicin directly into the middle ear. Seven days after the injection, it was possible to observe the degenerative process of the glycocalyx and the ciliary interconnections. The first detectable change was a disarrangement of the cilia with a loosening of the interconnections. The ciliary membrane presented with an irregular appearance. The tip links connecting the tips of the stereocilia to their neighbours were also affected showing elongation or even disappearance. In the later stages of the degeneration process, the sensory hairs presented with different degrees of fusion whereafter they finally disappeared totally. These findings suggest that the glycocalyx acts to maintain a normal stability and shape of the ciliary membrane and to keep the regular distance between cilia in order to maintain the arrangement of the whole ciliary bundle. Gentamicin probably affects the glycocalyx and the ciliary interconnections resulting in a disarrangement, detachment and fusion of cilia. The tip links, which are suggested to be involved in sensory cell transduction, seem to be also affected by gentamicin.