Abstract
Changes in the utricle and crista ampullaris epithelia in streptozotocin-induced diabetic rats and the influence of diabetes on gentamicin ototoxicity were examined using scanning and transmission electron microscopy. Diabetic rats showed utricular surface damage indicating degeneration of sensory cell cilia, at 8 months after a single injection of streptozotocin, whereas same aged non-diabetic rats showed no damage. The influence of diabetes on gentamicin ototoxicity to both utricle and crista epithelia was clearly demonstrated as revealed by the increase in severity of damage. The extent of utricular damage in non-diabetic rats as indicated by sensory hair degeneration was 16% of the sensory region, whereas that of diabetic rats injected with gentamicin after 7 months of induced diabetes was significantly extended to 42%. The striated organelles, the Friedmann body, were found in both types of sensory cells of only the diabetic rats. In cases where high blood glucose levels were maintained in the animals, the type I hair cells were almost completely destroyed by gentamicin. Type II hair cells remained but their sensory hairs were lost. As mentioned above, ototoxicity of gentamicin to the vestibular organ was enhanced in diabetes mellitus. As such, aminoglycoside should be used with caution in cases of infectious disease complicated by diabetes.
