Langendorff protocol

The protocol is approved by the Institutional Animal Care and Use Committee (IACUC). Isolated Langendorff-perfused hearts are used. White female New Zealand rabbits with a weight of 2-4 kg are anesthetized with 6 cc (50 mg/kg) Pentobarbital into the marginal ear vein. This causes little discomfort and no pain to the animal. To prevent blood coagulation 2 cc (2000 USP units) of Heparin are additionally given intravenously. The chest is opened, the pericardium removed and the heart excised from all veins and arteries. Immediately the heart is set up on the Langendorff apparatus. The ascending aorta is attached to the perfusion tube. The perfusion-solution, Hepes buffer, oxygenated (95% O2-5% CO2), at 37°C, pH titrated to 7.4, flows retrograde through the aorta to the coronary artery in order to nourish the heart. Perfusate is pumped through the device by means of a peristaltic pump. In experiments involving optical fluorescence, the heart is stained with a fast-response fluorescent dye. Both normal spontaneous sinus rhythms and paced rhythms are recorded. VF may be induced to the heart model by means of 50/60 Hz stimulation, T-shock, trains of diastolic stimuli and drugs (calcium chloride, dobutamine, isoprenaline, milrinone, etc.). The signal is digitized and stored on a MAC Quadra 650.