Biochemical heterogenity of the left ventricular myocardium: transmural and base-apex gradients on H.E.P. contents of the well oxygenated perfused dog heart.

An investigation into the contents (mumol/g w.w.) of the creatine phosphate (CP) and adenosine triphosphate (ATP) of various myocardial regions was performed on the empty beating isolated blood perfused dog heart. Across the myocardial wall, CP concentration was higher in the outer portion (9.03 +/- 0.18) than in the inner portion (8.59 +/- 0.20) (P less than 0.05). In addition to this transmural gradient, a longitudinal gradient was found: tissue contents of both CP and ATP decrease significantly from the base (CP: 9.70 +/- 0.28, ATP: 5.84 +/- 0.20) to the apex (CP: 8.69 +/- 0.27, ATP: 5.57 +/- 0.17) (P less than 0.01 and P less than 0.05 respectively). The gradients of metabolites in the well oxygenated empty beating heart suggest that a permanent metabolic adaptation to less adequate regional O2 reserves is physiologically operating in the subendocardial layer and the apex region of the left ventricle.