ABSTRACT
<p><b>AIM</b>To approach the protective effect of low dose gentamicin against high ototoxic dose of gentamicin.</p><p><b>METHODS</b>The guinea pigs were randomly divided into four groups: control group, low dose group, low dose protective group and high dose group. Each group received multiple intraperitoneal injections of gentamicin sulphate within different durations. Auditory brain stem response (ABR) was examined one day previous to the first and 24 h after the final injection respectively. The bulla was taken out so that the content of NO, MDA and the activity of LDH in cochlear were determined.</p><p><b>RESULTS</b>The threshold of ABR was significantly lower in low dose protective group compared with high dose group (P < 0.01). The content of NO (15.86 +/- 1.98 nmol/mg pro) and MDA (19.14 +/- 0.96 nmol/mg pro) in homogenate of high dose group was significantly higher than that of control group, low does group and low does protective group (P < 0.01). The increase of the content of NO and MDA induced by high dose GM could be significantly decreased by low dose GM administration previous to high dose injection (P < 0.01). The activity of LDH in homogenate of high dose group was significantly higher compared with control group, low dos group and low dos protective group (P < 0.01). There was no statistically significant difference of content of NO and MDA among control group, low does group and low does protective group.</p><p><b>CONCLUSION</b>The protective effects resulting from previous low dose administration to high dose injection of GM may be related to the decrease of content of NO and MDA and activity of LDH both of which induced by high dose GM.</p>