Myosin light chain phosphorylation during regional myocardial ischemia

The extent of cardiac myosin light chain phosphorylation was measured during regional myocardial ischemia in the dog. A multiple-projectile cutter was used to sample adjacent biopsies from the normal and ischemic areas of the myocardium in an open-chested dog heart following 30 min of coronary artery ligation. Measurement of metabolite levels and blood flow in the individual biopsies clearly defined the border zone between normal and ischemic myocardium. Myosin light chain phosphorylation was measured after isoelectric focusing of biopsy samples and subsequent densitometric analysis. A 50% increase in phosphorylation was observed in the ischemic zone which may correlate with the reduced contractility which is a feature of the ischemic myocardium.