Oxygen Consumption of Arterial Smooth Muscle as a Function of Active Tone and Passive Stretch

Abstract

The mean oxygen consumption of relaxed isolated vascular smooth muscle segments was found to equal 0.61±0.94 SEM µliter/mg wet wt/hr in a medium of buffered Ringer-glucose, and 0.65±0.05 SEM uliter/mg wet wt/hr in a solution of dog plasma. The resting muscle RQ was found to equal 0.99±0.01 SEM in buffered Ringer-glucose solution. When stimulated by addition of epinephrine the muscle segment contracted on the average by 9% of its initial diameter with a corresponding increase of its oxygen consumption by an average of 30% over its relaxed value. It was noticed that with increased initial circumferential stretch of the muscle segment, the amplitude of contraction was much greater when a given amount of catecholamine was added. This increase of sensitivity to catecholamine produced by initial stretch, was accompanied by a parallel increase of oxygen consumption by the contracted muscle. A qualitative correlation between an estimated degree of contraction of arterial muscle and its oxygen consumption was demonstrated. More quantitative correlation will have to depend upon better methods of measuring both the tension developed and the degree of initial stretch.