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Supramaximal Intensity Hypoxic Exercise and Vascular Function Assessment in Mice
Published on: March 15, 2019
Chronic hypoxemia increases myocardial cytochrome oxidase
David A Piel1, Azeem R Khan, Robert Waibel
1Department of Anesthesiology and Critical Care Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pa, USA.
The Journal of Thoracic and Cardiovascular Surgery
|October 11, 2005
Summary
Chronic hypoxemia increases cytochrome oxidase I expression and activity in newborn piglets. This adaptation may help preserve organ function during low oxygen conditions.
Area of Science:
- Biochemistry
- Physiology
- Cardiovascular Research
Background:
- Cyanotic heart disease can lead to reduced tissue oxygen tension.
- Cytochrome oxidase is crucial for cellular energy production, with subunit I encoded by mitochondrial DNA.
- Understanding adaptations to hypoxemia is vital for managing cyanotic patients.
Purpose of the Study:
- To investigate the impact of chronic hypoxemia on cytochrome oxidase subunit I (COI) in the ventricles of newborn swine.
- To assess changes in COI mRNA and protein expression and overall cytochrome oxidase activity.
Main Methods:
- A newborn swine model was used, creating chronic hypoxemia via a pulmonary artery-to-left atrium shunt.
- Ventricular COI mRNA and protein levels were quantified using Northern blot and immunoblotting.
- Cytochrome oxidase activity, heme content, and turnover number were measured.
Main Results:
- Hypoxemic piglets exhibited significantly lower arterial oxygen partial pressure and higher hematocrit.
- Chronic hypoxemia led to a >1.4-fold increase in ventricular COI mRNA and protein expression.
- Cytochrome oxidase activity increased 2.5-fold, with a 1.5-fold rise in heme content and turnover number.
Conclusions:
- Chronic hypoxemia upregulates COI expression and enhances cytochrome oxidase activity in the heart.
- Increased enzyme content and catalytic efficiency contribute to the observed kinetic changes.
- These adaptations may serve a protective role in maintaining cardiac function under hypoxemic conditions.
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