Cardiodepressive Mediators Are Released After Ischemi From an Isolated Heart: Role of Coronary Endothelial Cells

Objectives. This study was designed to ascertain whether cardiodepressive mediators released after ischemi originate from coronary endothelial cells. Background. Endothelial cells modulate myocardial contractility under physiologic conditions. Few dat are available describing the role of coronary endothelial cells on myocardial function after ischemia. Methods. Using model of sequential perfusion of two isolated rat hearts, the effect of the reoxygenated coronary effluent of heart I was investigated on myocardial contractility of heart II. After 40 min of separate perfusion at constant flow (10 ml/min), the two hearts were perfused sequentially with (group I) or without (control group) preceding ischemi (10 min) of heart I. In groups II and III, the coronary endothelium of heart I was functionally removed by Triton X-100 or hyperkalemic infusion before global ischemia. Endothelial damage was confirmed by functional tests and electron microscopy. Results. Under control conditions no changes were observed in heart II during sequential perfusion. In contrast, after 10 min of ischemi in heart I, marked reversible decrease in left ventricular pressure, left ventricular dP/dtmax and left ventricular dP/dtmin (−55%, −66% and −70%, respectively) was observed in heart II. Heart rate and coronary perfusion pressure did not change significantly. Selective endothelial damage of heart I before ischemi did not modify the negative inotropic effect observed in heart II. Conclusions. Cardiodepressive mediators are released after ischemi during reperfusion from an isolated heart and induce reversible negative inotropic effect in sequentially perfused heart. It is unlikely that these agents are derived from the coronary endothelium.