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Acta Otolaryngol. 2006 Dec;126(11):1134-9.

Ageing evokes an intrinsic pro-apoptotic signalling pathway in rat cochlea.

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  • 1Unidad de Investigación, Hospital Universitario de Getafe, Madrid, Spain.

Abstract

CONCLUSIONS:

These findings support the hypothesis that age-related apoptosis evokes an intrinsic pathway of pro-apoptotic signalling within the rat cochlea.

OBJECTIVES:

The aim of this study was to explore the effects of ageing on cochlear apoptosis in rats, as well as the different signalling pathways involved.

MATERIALS AND METHODS:

Female Sprague Dawley rats of different ages were used (mean age 7.72+/-1.93 months, n=100). Luciferase assays were used to determine the different caspase activities and ATP levels in rat cochlear protein extracts. Protein and gene expression was examined by Western blotting and real-time RT-PCR assays, respectively.

RESULTS:

Caspase-3/7 activity, as well as caspase-3 gene expression, were statistically higher in early-mature rats (EM, 276,139+/-13 669 RLUs (relative light units), p<0.001; and 390+/-50 arbitrary units, p=0.0017, respectively) or in aged-mature rats (AM, 371,020+/-26,457, p<0.0001; and 1510+/-90, p<0.0001, respectively) than younger rats (YR 147,129+/-8485 and 0.14+/-0.004, respectively). An increased caspase-9 activity with ageing was also observed (YR 49,932+/-2046 RLUs vs EM 260,890+/-5939, p<0.0001 or AM 118,241+/-12,423, p<0.0001). Caspase-8 activity was not affected significantly by age. Bax protein expression also increased by age (YR 38,200+/-1790 arbitrary units vs EM 76,549+/-5450, p<0.05), in contrast to Bcl-xL protein expression (YR 27,000+/-5000 arbitrary units vs EM 10,200+/-5000, p<0.005).

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