Effect of immediate and long term amino acids mixture administration on the mechanical performance and apoptotic parameters in isolated rabbit heart during ischemia reperfusion injury

ABSTRACT

Optimization of the post-ischemic myocardial function remains an elusive goal. The aim of this study was to investigate the effect of supplementation of a specific mixture of amino acids on ischemia and reperfusion induced damage in isolated rabbit heart. Four groups were included in this study groupl [control group] with isolated hearts perfused with Krebs-Henseleit solution for 2 h, group2 [ischemia-reperfusion group], group 3 [immediate amino-acids group] in which the hearts were perfused with the specific amino-acids mixture added to Krebs solution and group 4 [long term amino-acids group] this group received oral amino-acids mixture for 25 days before decapitation. The isolated hearts of group 2, 3 and 4 were subjected to 30 minutes pre-ischemic perfusion then 30 minutes of ischemia followed by 60 minutes of post-ischemic reperfusion using the Langhendorff technique and cardiac developed pressure, diastolic pressure, contractility index [dp/dt] and heart rate were measured during these phases as well as in group 1 at the end of 2h perfusion. Creatine kinase [CK] was measured in the collected cardiac perfusate at the end of the ischemic phase. Apoptosis was assessed in the heart by measurement of Pas protein level in heart tissue at the end of post-ischemic reperfusion using Elisa and by histological examination of the heart using the light and electron microscopes. Immediate perfusion of the heart with the amino acid mixture in group 3 significantly improved its pre-ischemic developed pressure with a median of 169mmHg compared to that of group 1 [88.5mmHg], group 2 [81mrnHg] and group 4 [99mmHg]. Long term amino acids supplementation in group 4 increased insignificantly its pre-ischemic developed pressure compared to that of group 1 and 2 while it increased significantly group 4 developed pressure with a median of21mmHg compared to that of group 2 [6mmHg] during ischemia.However the developed pressure in group 3 and 4 didn't show any significant change compared to group 1 and 2 during the whole period of post-ischemic reperfusion. Moreover the rise in the diastolic pressure during the post-ischemic reperfusion phase at 10, 30 and 60 minutes was significantly reduced in group 3 with a median of 21.5mmHg at 10 minutes, 19mmHg at 30 minutes and 15.5mmHg at 60 minutes; also it was significantly reduced in group 4 with a median of 13 mmHg at lOmin, 15.75mmHg at 30min and 10,75mmHg at 60min as compared to group 2 diastolic pressure median which was 37.5mmHg at lOmin, 36.25mmHg at 30min and 35.5mmHg at 60min. However there was no significant change in the diastolic pressure during pre-ischemic and ischemic phases in group 3 and 4 compared to group 2. Moreover group 3 and 4 showed no significant change in the pre-ischemic, ischemic and post-ischemic dp/dt contractility index and in the heart rate compared to group 1 and 2. The creatine kinase as a parameter of cardiac ischemia was insignificantly reduced in group 3 and 4 compared to group 2. While Fas protein level as an index of apoptosis showed a significant decrease in group 4 compared to group 2 and 3. Light and electronic microscopic examination revealed a significant improvement in the apoptotic features in group 3 and 4 compared to group 2 with normal nuclear size with condensed chromatin in H and E. Nuclei in group 4 were closer in appearance to those of the control group with normal mitochondria. In conclusion both immediate and long-term amino acids improved the cardiac performance, improved myocytees survival through decreasing Fas activation in cardiac cells during myocardial ischemia-reperfusion and reduced ischemia-reperfusion damage suggesting that mixed amino acids supplementation may be clinically useful as adjunct to conventional anti-ischemic agents.