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Age-related changes in G proteins in rat aorta
S L Mader1, C L Downing, J Amos-Landgraf
1VA Medical Center and Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
Summary
Aging impairs blood vessel relaxation due to reduced stimulatory G protein (Gs) function, not a loss of Gs protein levels. This suggests decreased cholera toxin labeling indicates functional decline in aged vessels.
Area of Science:
- Cardiovascular Physiology
- Molecular Biology
- Aging Research
Background:
- Aged blood vessels exhibit diminished relaxation in response to beta-adrenergic stimulation.
- This impairment may stem from alterations in G protein signaling, specifically stimulatory G protein (Gs) or inhibitory G protein (Gi).
Purpose of the Study:
- To investigate age-related changes in G protein levels and function in blood vessels.
- To determine if a loss of Gs or an increase in Gi contributes to impaired vascular relaxation in aging.
Main Methods:
- Studied aortic membranes from Fischer 344 rats across four age groups (6 weeks to 24 months).
- Assessed G protein levels using cholera toxin (labels Gs alpha) and pertussis toxin (labels Gi alpha) labeling.
- Quantified specific G protein subunits (Gs alpha, Gi alpha, G beta) via Western blotting.
Main Results:
- Cholera toxin labeling significantly decreased with age, from 6 weeks to 6 months, and remained low in older animals.
- Pertussis toxin labeling showed only a minor age-related decline.
- Western blotting revealed no significant changes in the protein levels of Gs alpha, Gi alpha, or G beta with age.
Conclusions:
- The decline in cholera toxin labeling with age does not correlate with a reduction in Gs alpha protein levels.
- These findings suggest that reduced cholera toxin labeling in aged vessels is a marker for impaired Gs alpha function, rather than a decrease in protein quantity.