Evidence for Direct Control of Coronary Vascular Tone by Oxygen
The interaction between the effects of oxygen and adenosine on acetylcholine-induced contractile tension was observed in helical coronary arterial strips suspended in physiological salt solution. It was found that (1) steady-state contractile tension was unaffected or depressed 5-20% when oxygen pressure (Po2) was diminished to levels as low as 5-10 mm Hg, (2) contractile tension was markedly depressed at a Po2 of 0 mm Hg, (3) adenosine-induced relaxation of contractile tension was inversely proportional to Po2 in the tissue bath, and (4) in the presence of adenosine at a concentration just adequate to inhibit contractile tension at a Po2 of 10 mm Hg, contractile tension was directly proportional to bath Po2. The latter two observations were usually most apparent at a Po2 between 10 and 40 mm Hg. It is proposed that the vasodilating effect of adenosine on the intact coronary vasculature may be most effective during myocardial hypoxia and that physiological control of coronary vascular tone may be more closely related to variations in local Po2 than to variations in local concentrations of adenosine.
- critical Po2
- rabbit arteries
- local control of blood flow
- metabolites and myocardial hypoxia
- Received August 16, 1972.
- Accepted November 21, 1972.
- © 1973 American Heart Association, Inc.