[Sensitivity to the ototoxicity of kanamycin of the rat model for mimetic aging in the inner ear].

Objective: To research the animal model with mimetic aging effect in the inner ear predispose to the ototoxicity of kanamycin.

Methods: Fifty wistar rats were randomly divided into four groups: group A (D-galactose group, n = 14) were treated with hypodermic 5% D-galactose (150 mg x kg(-1) x d(-1)) for 8 weeks and then with intraperitoneal saline for 10 days; group B (D-galactose and kanamycin group, n = 14) were given the same dose of D-galactose but kanamycin (500 mg x kg(-1) x d(-1)) instead of saline; group C (kanamycin group, n = 12) were treated with saline for 8 weeks and then with intraperitoneal kanamycin for 10 days;group D (control group, n = 10) were given saline only. Auditory brainstem response (ABR) was used to detect the hearing threshold of rats and colorimetry was used to analyze the activity of the GSH-PX. The inner ear tissue was harvested and the mitochondrial DNA was amplified to identify the 4834 bp deletion mutation by nested primer polymerase chain reaction (nested PCR) technique.

Results: The incidence of mitochondrial DNA 4834 bp deletion mutation was 100% (28/28) in group A, 92.86% (26/28) in group B and 0% in group C or group D. The activity of GSHPX in group A was (59.07 +/- 8.70)U, (63.29 +/- 12. 40)U in group B, (136.67 +/- 9.53)U in group C and (142.10 +/- 7.02)U in group D. The difference between group A and D was significant (P = 0.000) while the difference between group A and B was not significant (P = 0.307), which was similarly as between group C and group D (P = 0.151). ABR threshold was (5.36 +/- 3.08) dB peSPL in group A, (61.79 +/- 11.20) dB peSPL in group B, (34.17 +/- 4.69) dB peSPL in group C and (6.50 +/- 3.37) dB peSPL in group D. No difference was found between group A and D (P = 0.398) while the difference in shift of ABR threshold between group B and group C (or group D) was significant (P = 0.000).

Conclusions: The mimetic aging effect in the inner ear of the rat can be induced by D-galactose, and these rats present high incidence of mtDNA4834 deletion which can greatly enhance the sensitivity of the inner ear to the kanamycin.