An Assessment of Cochlear Hair-Cell Loss in Insulin-Dependent Diabetes Mellitus Diabetic and Noise-Exposed Rats

OBJECTIVE: The purpose of this study was to investigate if insulin-dependent diabetes mellitus causes degenerative changes in the inner ear and whether these changes are exacerbated by noise exposure. METHODS: Insulin-dependent diabetes mellitus was induced in male rats using streptozotocin (65 mg/kg of body weight, intravenously). Half the animals were exposed to 95 dB of random noise for 12 hours per day over a period of 6 months. The cochleae were removed, fixed, decalcified, dissected, and the hair cells counted. RESULTS: A significant loss of outer hair cells was exhibited in both noise-exposed groups; however, although there was no significant difference between these two groups, the noise-exposed diabetic animals had significant loss in more turns than did the noise-exposed control animals. The diabetic animals were not statistically different from the control animals. CONCLUSION: These results suggest that insulin-dependent diabetes mellitus may increase the hair-cell loss caused by noise overstimulation.