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Mary L. Garcia Cazarin, Miguel E. Andrade, Francisco H. Andrade; Age Does Not Affect Mitochondrial Respiration In Rat Extraocular Muscle. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1564.
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Extraocular muscles (EOMs) have unique metabolic adaptations to meet the demands imposed by their continuous activity. EOMs also have a high incidence of age-related mitochondrial mutations and are preferentially affected by mitochondrial myopathies such as chronic progressive external ophthalmoplegia. For this study, we tested the hypothesis that age alters mitochondrial respiration, the content of respiratory complexes and uncoupling proteins in rat EOMs.
We isolated mitochondria from EOMs of 6, 18 and 30 mo-old Fischer 344-Brown Norway F1 male rats to evaluate the effects of age on: (a) mitochondrial respiration by polarography; (b) thecontent of respiratory complexes, uncoupling proteins 1, 2 and 3 (UCP1, UCP2, UCP3), and voltage dependent anion channel 1 (VDAC1) by western blotting.
With the exception of state 2, there was no significant age effect on the mitochondrial respiration rates. State 2 respiration was lower at 18-mo compared to 30-mo (23.4±4 vs. 36.3±3 nmol O2/min/mg, respectively, p<0.05). The content of complexes I and IV decreased with age (complex I decreased 20% and 10% in 18 and 30-mo respectively; complex IV decreased 30% in 30-mo rats, all comparisons vs. 6-mo, p<0.05). The content of complexes II, III and V was not affected by age. UCP1, UCP3 and VDAC1 content increased 20%, 30% and 29% respectively by 30-mo compared to 6-mo (p<0.03 for all comparisons). UCP2 content did not change with age.
Mitochondrial respiration was minimally affected by age in the rat EOMs, despite the decrease in complex I and IV content. It is possible that the age-associated increase in VDAC1 content compensates for the change in respiratory complex content and sustains normal mitochondrial respiration. The observed increase in UCP1 and UCP3 content may reflect a need for greater protection against mitochondria-derived reactive oxygen species.
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