Experimental study on enzyme distribution and its relation to myocardial ischemic changes following coronary circulatory disturbances.

Coronary artery ligation of canine heart was performed to investigate the relationship between the lactate dehydrogenase (LDH) pattern in myocardium and the distribution of coronary flow, especially in the early stage of ligation and after reperfusion. In the myocardium of normal dogs, the LDH pattern was similar in the left ventricle, the interventricular septum, and the right ventricle; the average LD5:LD4 ratio was 1.1, 1.2, and 1.2, respectively, and consisted mainly of heart type. In the left and right auricles, however, the ratios were 0.3 and 0.2, respectively, lacking heart type. In the left ventricle, LD5:LD4 ratio in the subendocardium was different from that in the subepicardial layer. Blood flow distribution in canine myocardium was investigated by the fluorescent pattern on the cut surface of heart, in which 10% fluorescein sodium was injected into the cavity. By this method the evolution of the ischemic area from the endocardial layer to the epicardial side following coronary artery ligation and the effect of reperfusion on the ischemic area were clarified. Electron microscopic studies indicated that loss of mitochondrial function may account for the irreversibility of myocardial cell alteration. A new method for studying enzyme localization in tissues was introduced for studying LDH isoenzyme distribution in normal and injured myocardium.