Evidence for Direct Control of Coronary Vascular Tone by Oxygen

Abstract

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.