Expression of Rac1 in normal and gentamicin-induced ototoxic damaged cochlea of guinea pigs / 中国医师杂志

ABSTRACT

Objective To investigate the expression of Rac 1 in the guinea pig cochlea of gentamicin-induced ototoxic damage and prevention with antioxidant sodium salicylate , and to explore the roles of Rac 1 in the ototoxic mechanism of aminoglycoside antibi-otics.Methods Thirty healthy male guinea pigs were involved in this study .All the guinea pigs were randomly divided into 3 groups and received intraperitoneal injections according to their arranged group .Group I (control) was treated with normal saline for 7 days. Group II [Gentamicin (GM)] was treated with gentamicin alone for 7 days.Group III [GM+sodium salicylate(SA)] was treated with gentamicin in combination with sodium salicylate for 7 days.Paraffin-embedded cochlear section with immunohistochemical stai-ning was used for evaluation of Rac 1 expression in the cochlea .The protein was extracted from the cochlea tissues , and Rac1 protein levels in the cochlea were detected by Western blot assay .Results Immunohistochemistry showed a slightly positive reaction for Rac 1 staining found in the cochlea of the control group was mainly shown in the cytoplasm and cytomembrane of ganglion and organ of Corti ;a highly positive expression was shown in GM group;and the extent of Rac 1 expression of GM+SA group was between the control and GM groups.Image analysis showed that the differences in Rac1 expression between each two groups were statistically significant ( P <0.05).Western blot assay showed that expression of Rac 1 protein was highest in GM group and decreased in GM +SA group, while the intensity of Rac1 protein expression in GM +SA group was between the control and GM group .Statistics analysis showed that the expression between each two groups had significant difference ( P <0.05 ) .Conclusions A slightly positive reaction for Rac 1 stai-ning was found in the cochlea of guinea pigs , and mainly observed in the cytoplasm and cytomembrane of spiral ganglion and organ of Corti.With the administration of gentamicin , Rac1 protein expression was upregulated in the cochlea .Simultaneous administration of antioxidant sodium salicylate could significantly decrease the expression of Rac 1 protein.These results indicated that Rac1 might play an important role in the processes of gentamicin-induced oxidative damage of cochlea .