ABSTRACT
Iwould like to reflect a bit on the metabolic aspects. Metabolism underlines much of our thinking: metabolism of calcium, oxygen, or some other substrates. Dr. Weiss’s presentation this morning impressed me with two things. One is that the propranalol administration results in the disappearance of regions of very low oxygen, even in the ischemic zone, so that there was a more or less normal range of PO2 , despite the ischemia. Metabolism must have diminished in order to allow this. This reemphasizes the point that metabolism is a driving force for flow. The other point is that there is an important relationship between receptor abundance and the capacity to increase flow when stimulated, even though the association between regional receptor abundance and flow in normals is small. Regulation of local flow in the myocardium is a multifactorial business. Further, the range of flows in the normal myocardium is so broad that it demands some kind of explanation. This more or less sixfold range of flow is very provocative.
