Actions of a Dopaminergic and β2-Adrenergic Agonist on O2 Extraction by Canine Skeletal Muscle
In order for a tissue to extract O2 from a diminished supply as efficiently as possible, blood flow must be directed within the tissue proportionately to regional O2 demand. This is accomplished by a balance of vasoconstrictor and vasodilator forces. If O2 supply is lowered in the whole body, vasoconstrictor tone is increased by increased activity of sensors such as baroreceptors or peripheral chemoreceptors. At the local tissue level, metabolic signals proportional to the imbalance between O2 supply and demand cause local dilatation to direct more blood flow to those areas and protect them from hypoxic injury. According to this scheme, any intervention that overrides either regulatory factor should be reflected in a diminished ability of the local tissue to extract O2 under hypoxic conditions.
KeywordsExtraction Ratio Arterial Inflow Peripheral Chemoreceptor Hypercapnic Acidosis Hypoxic Hypoxia
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