Effects Of Acidic Reperfusion On Isolated Aged Rat Heart Against Ischmia Reperfusion Injury

Objective (1)To observe the effects of prolonged transient acidosis on coronary flow and the pH of coronary effluent in aged rat heart after reperfusion injury.(2)To investigate the effects of acidic reperfusion on isolated rat heart against ischemia reperfusion injury and the role of PI3K signaling pathway in it.MethodsExperiment 1: Twenty-four aged SD rats,which were 18 months old,weighing 450-550g were randomly divided into 3 groups (n=8): reperfusion injury(C) group,ischemic postconditioning(IPO) group and acidosis(H+) group. The isolated rats hearts were passively perfused on a Langendorff apparatus with 37℃Kerbs-Henseleit buffer(KHB) saturated with mixture gas,which including 95%O2-5%CO2. The isolated aged rats hearts were made globally ischemia for 30 min at 37℃and followed by 120 min reperfusion with KHB(pH7.4) after each deal. The ischemic postconditioning group was performed by reperfused KHB(pH7.4) for 15 s followed by 15 s of suspension, repeated for 6 times at the beginning of reperfusion. In acidic reperfusion group was perfused Kerbs-Henseleit buffer of pH 6.9 (which was saturated with 80%O2-20%CO2 for 30 min) for 3 min respectively at the beginning of reperfusion;Observed the pH of coronary effluent before ischemic,at 3 min,5 min,8 min after reperfusion;and coronary flow before ischemic,at 3 min,10 min,30 min after reperfusion.Experiment 2: Seventy aged SD rats,which were 18 months old,weighing 450-550g were randomly divided into 7 groups (n=10): ischemia- reperfusion injury group (C); ischemic postconditioning group (IPO); acidic reperfusion group (H+);postconditioning+alkalotic reperfusion group (IPO + OH-); alkalotic reperfusion group (OH-); acidic+wortmannin reperfusion group (H+ + wort ); wortmannin reperfusion group (wort). The isolated rats hearts were passively perfused on a Langendorff apparatus with 37℃Kerbs-Henseleit buffer(KHB) saturated with mixture gas,which including 95%O2-5%CO2. The isolated aged rats hearts were made globally ischemia for 30 min at 37℃and followed by 120 min reperfusion with KHB(pH7.4) after each deal. The ischemic postconditioning group was performed by reperfused KHB(pH7.4) for 15 s followed by 15 s of suspension, repeated for 6 times. In acidic reperfusion group and alkalotic reperfusion group, Kerbs-Henseleit buffer of pH 6.9 (which was saturated with 80%O2-20%CO2 for 30 min) and pH 7.8(which was saturated with 100%O2 for 30 min) was perfused for 3 min respectively at the beginning of reperfusion; in group IPO + OH- was conducted ischemic postconditioning by KHB( pH7.8); in group H++wort and wort, 100 nmol/L wortmannin in KHB of pH6.9 and 7.4 was perfused for 3 min at the beginning of reperfusion. The hemodynamics parameters including heart rate(HR),left ventricular systolic pressure(LVSP),coronary flow (CF),and±dp/dtmax were monitored before ischemia and at 5,15,30min after reperfusion. The NO concentration in coronary enffluent and the NOS concentration in the left ventricular muscles were measured at 30 min after reperfusion. The hearts were stained by Triphenyltetrazolium chloride(TTC) and measured the myocardium infarct size through the percentage of the ischemia area(IS) in the area at risk(AAR) after 120 min reperfusion.Results(1)Compared with the pH of coronary effluent,there were no difference in the three groups before ischemic(P>0.05).The pH value of coronary effluent were decreased in IPO group and H+ group,compared with C group at 3min after reperfusion(P<0.05). The pH of coronary effluent were no difference between the three groups at 5min and 8min(P>0.05). Compared with C group,the coronary flow were increased at 3min,10min and 30min in IPO group and H+ group after reperfusion(P < 0.05).There were no difference between the two groups.(2) There no difference between the indexs in each groups before ischemia (P>0.05).The HR,LVSP,CF and±dp/dtmax were increased , the myocardium infarct size was smaller, the NO concentration in coronary enffluent and the NOS concentration in myocardium tissue were higher in group IPO and H+ than those in group C after reperfusion(P<0.05 or 0.01). The myocardium infarct size were larger in group OH-,H++wort and wort,comparing with group C (P<0.05 or 0.01)and no difference between other index(P>0.05).There were no difference between group IPO and H+ by comparing with the hemodynamics parameters,the myocardium infarct size,the NO concentration in coronary enffluent and the content of NOS in the left ventricular muscles(P>0.05).Conclusion (1)Reperfused with low pH for 3 min have the same effect on coronary flow and pH value of coronary effluent as well as postconditioning on isolated aged rat hearts. (2)Acidic repersusion can attenuated the ischemia- reperfusion injury in isolated aged rat heart just as the same to the ischemic postconditioning, and PI3K signaling pathway maybe involved in the protective effect.