Isolated rat heart perfusion and Langendorff procedure

20 Rats were anesthetized with sodium pentobarbital (50 mg/kg i.p.). A thoracotomy was then performed and hearts were rapidly excised into an ice-cold K-H solution. After removal of the lungs and surrounding tissues, the aorta was attached to the perfusion device where hearts were perused at a constant retrograde flow, according to the method of Langendorff with a non-recirculated K-H solution, gassed with carbogen (95% O₂ and 5% CO₂) at 37 °C to obtain a physiological pH of 7.4. The hearts were perfused with constant pressure of approximately 65 mmHg and left for 20 min to permit recovery of function and stabilize the rhythm. The left ventricular end diastolic pressure was maintained at 5–10 mmHg, and cardiac function was evaluated by measuring left ventricular developed pressure (left ventricle end systolic pressure minus left ventricle end diastolic pressure; LVDP = LVSP − LVEDP), maximal and minimum rate of pressure development (±dp/dt_max), and heart rate (HR). LVDP, ±dp/dt_max, and HR were calculated from the left ventricular pressure curve. These parameters were recorded continuously on a computer using Powerlab data acquisition system (8SP Chart 7 software; A.D. Instruments, Castle Hill, Australia)⁵³.

Hearts were then randomly assigned to the following groups: (1) Control group (hearts perfused with K-H buffer for 120 min); (2) I/R group (hearts that were allowed to stabilize for 30 min prior to being subjected to 30 min global ischemia achieved by discontinued K-H buffer perfusion, followed by 60 min reperfusion); (3) QSYQ group (hearts perfused with QSYQ 0.2 mg/mL for 10 min after 20 min of stabilization, global ischemia for 30 min, followed by 60 min reperfusion); (4) QSYQ-DO group (hearts perfused with QSYQ-DO 0.2 mg/mL for 10 min after 20 min of stabilization, global ischemia performed for 30 min, followed by 60 min reperfusion) and DO group (hearts perfused with DO volatile oils 0.2 mg/mL for 10 min after 20 min of stabilization, global ischemia performed for 30 min, followed by 60 min reperfusion).