Circulatory Effects of Tissue Oxygen Tension Sensors
There is no disagreement that in practically all tissues hypoxia results in vasodilation and in muscle such as the heart hypoxia is undoubtedly the most potent physiological vasodilator. The unresolved question, and one that has attracted the attention of investigators for many years is the mechanism whereby an inadequate oxygen supply for the tissue needs elicits relaxation of the smooth muscle of the resistance vessels. In 1925 Hilton and Eichholtz1 performed experiments with the dog heart-lung preparation in which they carried out a series of interventions such as reducing the oxygen content of the arterial blood, adding lactic acid, CO2 or cyanide to the arterial blood and changing to fresh blood after prolonged coronary perfusion that had resulted in progressive coronary vasodilation. On the basis of their findings they concluded that there were not significant amounts of “vasodilator metabolites” liberated from the myocardium and implied that the impressive inverse relationship between blood oxygen levels and coronary blood flow was due to a direct effect of oxygen lack.
KeywordsCoronary Flow Coronary Blood Flow Adenosine Deaminase Reactive Hyperemia Circulatory Effect
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