[Protective effects of N-acetylcysteine on cochlear damage occur in guinea pigs exposed to irradiation].

Objective: To explore the protective effects of N-acetylcysteine (NAC) on cochlear damage occurring in irradiated guinea pigs.
Methods: Seventy-two guinea pigs were randomly divided into 4 groups (n = 18 each). Control group received neither NAC nor irradiation, irradiation group received total cranium irradiation of 70 Gy, irradiation & saline group cranium irradiation of 70 Gy and saline solution through a round window and NAC group cranium irradiation of 70 Gy and NAC through a round window. The right ear received radiation. The animals were sacrificed at Day 14 post-irradiation. The specimens were dehydrated, embeded in paraffin and serially cut into 5-µm slices. Sections were stained with immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL). The cochlear basal membranes were observed for malondialdehyde (MDA) and superoxide dismutase (SOD) with scanning electron microscope.
Results: The cilium of hair cells had no clear loss and apoptotic number of spiral ganglion cells decreased in NAC group. The average optical density value of Caspase 3 in spiral ganglion in NAC group significantly decreased versus the irradiation group (0.08 ± 0.02 vs 0.10 ± 0.01, P < 0.01). The level of MDA of NAC group also decreased versus the irradiation group (0.33 ± 0.05 vs 0.84 ± 0.13, P < 0.05). The level of SOD in the NAC group increased versus the irradiation group (10.7 ± 3.0 vs 8.7 ± 1.3, P < 0.05). The ratio of apoptotic cell in SGC in the NAC group at Day 14 (7.8% ± 1.8%) decreased versus the irradiation group (32.0% ± 8.7%) at Day 14.
Conclusion: MDA and SOD may be involved in the pathogenesis of cochlear cell damage. And NAC protects the irradiated cochlear cell.