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Changes in the rat liver mitochondrial DNA upon aging
K Asano1, S Amagase, E T Matsuura
1College of Medical Technology, Kyoto University, Japan.
Mechanisms of Ageing and Development
|November 1, 1991
Summary
Aging in rats alters mitochondrial DNA (mtDNA), causing it to bind proteins and resist digestion. These changes affect mtDNA
Area of Science:
- Molecular Biology
- Gerontology
- Mitochondrial Biology
Background:
- Aging causes significant morphological and functional changes in rat liver mitochondria.
- Understanding the molecular basis of these changes is crucial for aging research.
Purpose of the Study:
- To investigate molecular alterations in rat liver mitochondrial DNA (mtDNA) during aging.
- To identify changes in mtDNA properties and their potential causes.
Main Methods:
- Analysis of mitochondrial DNA buoyant density profiles.
- Electron microscopy for mtDNA morphology.
- Proteinase K treatment to assess protein binding.
- EcoRI digestion to evaluate DNA resistance.
Main Results:
- Mitochondrial DNA from old rats exhibited a broader buoyant density distribution, shifting towards lighter fractions compared to young rats.
- Proteinase K treatment partially normalized the mtDNA buoyant density profile in aged rats, suggesting protein association.
- Electron microscopy revealed that aged rat mtDNA could attach to negatively charged mica without magnesium ions, a property absent in young rat mtDNA.
- Mitochondrial DNA from old rats showed increased resistance to EcoRI digestion, unlike DNA from younger animals.
Conclusions:
- Mitochondrial DNA in aged rat liver likely contains firmly bound proteins or peptides.
- These bound proteins confer novel properties to aged mtDNA, including altered density, enhanced binding to charged surfaces, and resistance to enzymatic digestion.
- The observed changes in mtDNA properties during aging may be attributed to age-related protein modifications or associations.