Intracellular potential changes following coronary occlusion in isolated perfused rat hearts

A method of perfusing rat ventricles has been developed which permits the recording of intracellular potentials from up to 10 cell layers below the endocardial surface. Intracellular potentials from all layers remained the same for up to 1.5 h before occlusion. Regional occlusion of flow was produced by occluding the left anterior descending coronary artery and then intracellular potentials were recorded from normal and occluded cells for up to 2 h after occlusion. Immediately after occlusion, marked changes in potentials were recorded from occluded tissue. The greatest change was in the duration of the action potential which showed a marked shortening. There was also a reduction in the maximum rise rate and action potential height with smaller falls in resting membrane potential. Changes were greatest in the deeper cells (layers 6-10) and least in superficial subendocardial cells which were always superfused with perfusion fluid. Occlusion increased the number of quiescent cells (no action potential) as well as the number of cells showing aberrant action potential configurations (e.g., double peaks). Similar changes in intracellular potentials following occlusion were also recorded from the subepicardial surface of anaesthetized rats in situ. Arrhythmias induced by occlusion were similar to those seen in conscious rats following occlusion of a coronary artery.