Effect of erdosteine on radiation-induced cochlear damage in rats

Abstract

Oxidative stress has an important role in the pathogenesis of radiation-induced cochlear damage. We examined the effects of the antioxidant erdosteine (ERD) on this damage. Healthy rats (n = 92) were divided into four groups: control (C-g), erdosteine alone (ERD-g), radiotherapy alone (RT-g), and erdosteine + radiotherapy ((ERD+ RT)-g). Except for the C-g, all groups were further divided into the 1st day, 8th day, and 8th week subgroups for evaluating acute, subacute, and chronic radiation effects, respectively, on the cochlea. All rats underwent distortion product otoacoustic emission (DPOAE) testing before irradiation. The C-g received neither ERD nor radiation. The ERD-g and (ERD+ RT)-g received 10 mg kg(-1) day(-1) ERD orally 2 days prior to irradiation, and ERD was continued for 5 consecutive days during irradiation. RT-g and (ERD+ RT)-g received whole cranial radiation of 33 Gray (Gy) total in the form of 6.6 Gy/day on 5 consecutive days. After the last dose of radiation, rats were evaluated by DPOAE and then sacrificed at the relevant time point. DPOAE responses before and after irradiation were compared. Cochleas from the experimental groups were examined by light microscopy and were compared with those of the C-g. Both the DPOAE responses and the microscopic examination results were better in the (ERD+ RT)-g than RT-g (P < 0.05). However, progressive decreases in DPOAE responses at all studied frequencies were detected despite the use of ERD in the (ERD+ RT)-g. In conclusion, ERD reduced the degree of radiation-induced cochlear damage but did not prevent progression of the damage.