[The relationship between the fragment deletion of mtDNA in old rat and the sensitivity to aminoglycoside antibiotic induced deafness].
OBJECTIVE
To analyze the relationship between the fragnent deletion of mitochondrial DNA (mtDNA) of inner ear in rats and aminoglycoside antibiotic induced deafness (AAID), and to investigate the possible role of mtDNA deletion in the sensitivity to aminoglycoside antibiotic induced deafness in old rat.


METHODS
Thirty wistar rats were divided into group A (old rat, > 24 months, n = 15) and group B (young rat, 4 months, n = 15) according to the age. Kanamycin (KM) was intraperitoneally injected 500 mg/kg per day for 10 consecutive day in all rats. The threshold of the auditory brainstem response (ABR) was measured before and after the drug administrations. The inner ear tissue was harvested and the mtDNA was amplified to identify the 4834 bp deletion by PCR technique.


RESULTS
The elevation of the mean ABR thresholds in group A (42.08 +/- 8.19) dB peSPL was significantly higher than that in group B (12.71 +/- 4.42) dB peSPL (P < 0.01). In group A, 10 of the 15 rats demonstrate the mtDNA4834 deletion and the elevation of the mean ABR thresholds in the rats with mtDNA4834 deletion (45.00 +/- 7.67) dB peSPL was significantly higher than that without so deletion (33.33 +/- 4.08) dB peSPL (P < 0.01). However, mtDNA4834 deletion was negative in group B.


CONCLUSIONS
Deletion of mtDNA of inner ear tissue in old rat is found. The mtDNA deletion may play an important role in the hypersensitivity to aminoglycoside antibiotic ototoxiciy in old rats.
Liu
Jun
J
Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
Kong
Weijia
W
Liu
Weirong
W
Liu
Zhengrong
Z
D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D004272:DNA, Mitochondrial / Q000187:drug effects / Q000235:genetics*; D003638:Deafness / Q000139:chemically induced* / Q000235:genetics; D007758:Ear, Inner / Q000187:drug effects; D016057:Evoked Potentials, Auditory, Brain Stem; D017353:Gene Deletion; D007612:Kanamycin / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar
D000900:Anti-Bacterial Agents; D004272:DNA, Mitochondrial; D007612:Kanamycin