Transmural distribution of myocardial adenosine content during coronary constriction

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Abstract
The transmural distribution of tissue adenosine content was determined in samples of the left ventricle from anesthetized open-chest dogs. Transmural tissue samples were obtained and quickly freeze-clamped during either normal coronary perfusion or partial constriction of the inflow tubing of the left common coronary artery. Inner, middle and outer segments of the samples were assayed for adenosine, inosine, ATP, creatine phosphate and lactate. In control experiments, there were no significant differences among the tissue contents of the substances in the 3 segments. During a 50.2 .+-. 4.7% reduction of coronary inflow, adenosine content of inner, middle and outer segments was 0.41 .+-. 0.007, 0.030 .+-. 0.006 and 0.016 .+-. 0.003 nmol/mg protein, respectively. Outer segment content was significantly less than either middle or inner content. Lactate distribution was similar to that of adenosine; ATP and creatine phosphate were lowest in the inner segment. Increases of the inner/outer adenosine ratio occurred when the coronary-ventricular pressure index was lower than 1.2. Selective underperfusion of the subendocardium during reduced coronary inflow can result in greater accumulation of adenosine in that region.

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