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Calcium accumulating ability of mitochondria from bovine coronary artery. Comparison with aortic mitochondria
Insights
Mitochondria from bovine coronary arteries and aorta efficiently accumulate calcium. This study provides a method for isolating these mitochondria for further research on vascular smooth muscle.
Area of Science:
- Biochemistry
- Cell Biology
- Cardiovascular Physiology
Background:
- Mitochondrial calcium handling is crucial for vascular smooth muscle function.
- Understanding calcium uptake in vascular mitochondria is important for physiological and pharmacological studies.
Purpose of the Study:
- To investigate and compare the calcium accumulating ability of mitochondria from bovine coronary artery and aorta.
- To establish a reliable method for isolating vascular mitochondria with high calcium uptake capacity.
Main Methods:
- Isolation of mitochondria from bovine coronary artery and aorta using collagenase pretreatment.
- Assay of mitochondrial enzyme activities (cytochrome c oxidase, NADPH-cytochrome c reductase, etc.).
- Measurement of mitochondrial calcium uptake and sensitivity to metabolic inhibitors (NaN3, ruthenium red, 2,4-dinitrophenol).
Main Results:
- Isolation procedures yielded mitochondria highly enriched in cytochrome c oxidase activity.
- Mitochondria from both tissues exhibited significant calcium uptake activity, sensitive to metabolic inhibitors.
- Coronary artery mitochondria showed a faster calcium binding onset and higher azide sensitivity compared to aortic mitochondria.
Conclusions:
- A method for isolating vascular smooth muscle mitochondria with high calcium uptake capacity was successfully developed.
- Differences in calcium handling kinetics were observed between coronary artery and aortic mitochondria.
- These findings provide a foundation for future research into mitochondrial calcium regulation in vascular tissues.
Abstract:
The calcium accumulating ability of mitochondria isolated both from bovine coronary artery and aorta was investigated. Coronary artery and aorta were pretreated with 0.1% collagenase. Cytochrome c oxidase activities of mitochondria isolated from coronary artery and aorta showed 25-fold and 19-fold increases, respectively, as compared with those of each homogenate, whereas NADPH-cytochrome c reductase, potassium-phosphatase and Na+-K+ ATPase activities increased less than 2-fold. This suggests that the isolation procedure is capable of obtaining a subcellular fraction highly enriched with mitochondria. Mitochondrial calcium uptake activity of the coronary artery was approximately 250 nmoles Ca2+/mg protein/10 min, and was markedly depressed with metabolic inhibitors such as NaN3, ruthenium red and 2,4-dinitrophenol. Calcium uptake activity of bovine aortic mitochondria showed similar activity and a similar trend in sensitivity to metabolic inhibitors. By contrast, the onset of the calcium binding reaction of the aortic mitochondria was slower and the azide-sensitivity of the mitochondria to magnesium ATPase activity was lower than those for coronary artery mitochondria. The present study has provided a method for isolation of mitochondria with a high capacity of calcium uptake activity, which may prove meaningful for future physiological and pharmacological evaluation of mitochondrial calcium accumulation in vascular smooth muscle.