Contractility and energetics effects of ethanol and isoproterenol using an improved biologically stable isolated ejecting rat heart system

An isolated working rat heart perfusion preparation was designed to incorporate improved glass oxygenators, an in series aortic flow probe providing aortic flow and ejection velocity measurements, and a calibrated pressure volume apparatus for quantification of coronary flow and total cardiac venous effluent. Sustained biologic myocardial integrity was demonstrated in isolated hearts of Long Evans rats perfused antegrade with Krebs Henseleit bicarbonate buffer for 120 minutes with left ventricular (LV) filling and aortic reservoirs placed 10 cm and 80 cm, respectively, above the working heart. Heart rate, LV peak systolic and end diastolic pressures, LV dP/dt, stroke volume, aortic flow, peak ejection velocity, coronary flow, and myocardial oxygen consumption indicated that after 20 minutes perfusion in the recirculating antegrade system cardiac function and energetics remained stable for at least the subsequent 100 minutes. Cardiac creatine phosphate, ATP, lactate, and glycogen concentrations during the 120 minute period exhibited responses characteristic of well oxygenated working myocardium. Electron microscopy at conclusion of perfusion showed normal cardiac ultrastructural features without edema. Sensitivity to interventions of perfused hearts was documented by positive inotropic actions of isoproterenol (1 x 10 ^-8M) and cardiodepressant effects of ethanol (65 mM). Thus this modified antegrade perfusion system provides a highly stable working heart preparation for periods up to two hours for assessment of physiologic and metabolic alterations of myocardial performance induced by cardiovascular drugs.