[Mitochondrial DNA large deletions associated with presbycusis].

OBJECTIVE

By observing the relationship between the fragment deletion of mitochondrial DNA (mt DNA) of inner ear in rat and the hearing loss to investigate the possible role of mt DNA deletion in presbycusis.

METHOD: Thirty wistar rats were divided into group A (young rat, 4 months, n = 15) and group B (old rat, 24-30 months, n = 15) according to the age. The threshold of the auditory brainstem response (ABR) was tested. The inner ear membranous labyrinth tissue was harvested and the mtDNA was amplified to identify 4,834 bp deletion by PCR technique.

RESULT: The mean of ABR thresholds in group B (64.79 +/- 10.88 dB peSPL) was significantly higher than that in group A (40.00 +/- 4.66 dB peSPL) (P < 0.01). In group B, 9 of the 15 rats demonstrates the mtDNA 4,834 bp deletion, while no deletion was detected in group A.

CONCLUSION

Deletion of mtDNA of inner ear tissue in old rat is found. The mtDNA deletion is associated with the presbycusis and may be one of the causes of presbycusis.