[Changes in antioxidant capacity of the guinea pig exposed to noise and the protective effect of alpha-lipoic acid against acoustic trauma].

Abstract

The study was aimed at exploring the effect of noise on total antioxidant capacity (TAC) in serum, nitric oxide (NO) level in the cochlea and the protective action of alpha-lipoic acid against noise-induced hearing loss (NIHL). Sixty guinea pigs (350-400 g) were divided randomly into three groups (control group, noise+saline group and noise+alpha-lipoic acid group). Serum and cochlear tissue were treated immediately after noise exposure (4-kHz octave band, 115 dB SPL 5 h) to determine the level of TAC and NO, respectively. Auditory brainstem responses (ABRs) were measured before and immediately after exposure. The threshold of hearing in the control group was relatively stable, while the hearing threshold in the noise+saline group was significantly higher than those in the noise+alpha-lipoic acid group (P<0.05). TAC level of the noise+saline group was significantly lower than that of the control group P<0.05 . TAC level of the noise+alpha-lipoic acid group was significantly higher than that of the noise+saline group P<0.05 , while there was no significant difference in the levels between the noise+alpha-lipoic acid group and the control group (P>0.05). The NO level of the cochlear tissue in the noise+saline group was significantly higher than that of the control group (P<0.05). Cochlear NO level in the noise+alpha-lipoic acid group was significantly lower than that of the noise+saline group (P<0.05), while there was no significant difference in cochlear NO levels between the noise+alpha-lipoic acid group and the control group (P>0.05). The results obtained indicate that noise exposure causes a decrease in serum TAC and an increase in NO in cochlea. alpha-Lipoid acid exerts a protective effect against hearing loss in acoustic trauma through its antioxidant effects.