The Empirical Study Of The Protective Effects Of Adenosine On Myocardial Ischemical Reperfusion Injury In Rats

PrefaceContinuity myocardial ischemia can lead to cells ischemical injury, and recovering the blood to myocardial can aggravate the reciprocity ischemical injury or make it convert into irreversible damage, this kind of phenomenon is called myocardial ischemical reperfusion injury ( MIRI). Currently, the MIRI has become the main tough problem to bar the ischemia myocardial to acquire the best curative effect from reperfusing therapy. It is very important to research the medicine of the good protection function for it.The aim of this study is to detect the protection of adenosine on myocardial ischemical reperfusion injury of rats in vivo, through the model of myocardial ischemical/ reperfusion ( I/R) in the rats to approach possible mecha - nism of action.Material and MethodForty - two healthy Wister rats ( weight 250g ± 30g) were divided into 3 group randomly , each group had fourteen rats . The Set of Ⅰ 14 is sham operated group, the set of Ⅱ 14 is control group, the set of Ⅲ 14 is adenosine group. Manufacture the model of myocardial I/ R in rats. Sham operated group: Complete the model operation, wear the line and dont ligature the coronary artery only. Adenosine group: Complete the model operation , the coronary artery was ligatured for 30 minutes and reperfused for 45 minutes, 1 minute before ischemicto infuse the adenosine(0.4ml/kg) in left ventricle. Matched control; complete the model operation, the coronary artery was ligatured for 30 minutes and reper-fused for 45 minutes , then infuse the same quantity normal sodium in left ventricles at the same time. After experimenting being over, each one samples 2 randomly to make pathological section and the rest 36 are going to observe other index signs. ( 一) After ligatured for 30 minutes and reperfused for 45 minutes , execute the rats immediately and shear the ischemic region quickly about 0.1 g. Putting it in frosty normal sodium and rinsing it in order to remove the blood, then putting it into the 1.5 ml plastic centrifuge tube, preserving in refrigerators of -70℃. After completing experiment, take out all specimens to create 10% myocardial homogenate and take the 0. 5 ml supernatant to provide. ( 二) Each group samples 2 randomly in the experiment end, execute the rats immediately and take out the heart, put it in 4% formaldehyde quickly. Starting from the a-pex cordis with the interval of 0. 3 cm, to cut into slices horizontal to wear the line continuously. Using paraffin wraps to cover up the slice, number the slices for use.(一) Detect the SOD of left ventricles myocardial organization: xanthine oxidase method; The MDA compares ; TBA method. ( 二) The myocardial paraffin section with HE stain; observating morphologic change with optical microscope. (三) Statistics the incidence rate of ventricular tachycardia ( VT) in the period of reperfusion , ventricular fibrillation ( VF) and death ( the VF keeps on 3 minutes or longer and electrocardiosignal disappears for 30s). ( 四) the measurement of the left heart function; △ LVSP = LVSP ( before ischemic) -LVSP( reperfusion 45 minutes) ;LVEDP. Compare the A LVSP and the LVEDP. Statistical analysis; measurement data;t test, numeration data; X2 test.ResultsTow of forty - two rats died, both of them are control group . The rest all sentences to death immediately after experiment be over.1. The SOD and MDA compared in the myocardial organization; the vitality of SOD in control group descends obviously, the vitality of SOD in adenosinegroup boosts . The quantity of MDA in the control group is obvious higher than sham operated group , but the quantity of MDA in the adenosine group obvious less than the control group.2. The myocardial paraffin section with HE stain; there is obvious myocardial fiber break , necrosis , bleeding and inflammatory cell infiltrate in the control group; there is no necrosis and bleeding in the adenosine group and sham operated group ,but the cardiac muscle fiber in the adenosine group looks like waves, distribute of carcoplasm is not evenly, and find a little amount inflammatory cell infiltrate.3. The influence on arrhythmic of rats ; the occurrence rate of VT is 8. 3% of the sham operated, control group s is 83. 3% ; VF of control group is 41. 7% , death rate is 16.7% ; The adenosine group matched the control group relatively the VT occurrence the rate to descend 41. 6% , the VF occurrence descends 33.4% , the death rate descends 16.7%.4. The influence of adenosine on the left ventricles function: A LVSP of the control group and the LVEDP are obvious higher than those of adenosine group and sham operated.DiscussionMIRI has multiple factor and complicate mechanism. Intracellular Ca metabolic disorder , the oxygen free radicals and neutrophi infiltration main paths that results in the myocardial ischemia reperfusion injury. Penny has pointed out, producing of the oxygen free radicals is significant among them. A great deal of research express that the oxygen free radicals content increases obviously while myocardial ischemia reperfusion injury.The adenosine is one kind of endogenous protectant . Ad is mainly produced when the ATP degradation, the myocardial ischemia can cause ATP deg-radate to Ad immediately. The physiological effect of the adenosine is mostly mediated by adenosine receptor . There have four types: A1, A2a, A2b, and A3. The Study the confirmation, to give the exogenous adenosine imitating the adenosine releases after IP can protect the MIRI.We were successfully in manufacturing the rats' I/ R model, and the result showing: (1) The vitality of SOD in control group descends obviously, the vitality of SOD in adenosine group boosts . The quantity of MDA in the control group is obvious higher compared with sham operated group , but the quantity of MDA in the adenosine group obvious less compared with the control group. SOD is an important antioxidase inside the body . MDA is the lipid peroxidation outcome . As a result, lower of the SOD activity and MDA increment, expressed a great deal of growth of the oxygen free radicals, also reflected the degree that cell hurt indirectly.This experiment result explains that as the myocardial I/R there is a great deal of oxygen free radicals creation, causing the myocardial injury. But the a-denosine can inhibit the oxygen free radicals, the having the stronger anti - oxygenation , thus protecting the big rat I/ R myocardial. The mechanism of oxygen free radicals creation may be : ①Xanthine oxidase (XO) increase . ②The neutrophil activated . ③Chondrosome function damaged, the born free radicals increase. ④ Ischemic can stimulate the body to release a great deal of catecholamine, it' s oxidative product can produce the oxygen free radicals. The myocardial I/ R injury, producing a great deal of oxygen free radicals, can respond with various cell composition occurrence, result in the cell structure hurt and metabolic block.(2) The myocardial paraffin section with HE stain; there is obvious myocardial fiber break , necrosis , bleeding and inflammatory cell infiltrate in the control group; there is no necrosis and bleeding in the adenosine group and sham operated group ,but the cardiac muscle fiber in the adenosine group looks like waves, distribute of carcoplasm is not evenly and find a little amount inflammatory cell infiltrate. The result illustrated that MIRI can induce myocardial ischemia injury to aggravate, appearing the myocardial fiber to split, necrosis. But the adenosine contribute to maintaining the myocardial cell the normal appearance structure, having the function of protection to the myocardial of I/ R.(3 ) Reperfusion Arrhythmia ( RA) is most frequent in the myocardial I/ R . This experiment result show the occurrence rate of VT is 8. 3% of the sham operated, control group's is 83.3% ; VF of control group is 41.7% , death rateis 16. 7% ; The adenosine group matched the control group relatively the VT occurrence the rate to descend 41. 6% , the VF the occurrence descends 33.4% , the death rate descends 16.7%. Its mechanism is increase by the calcium inside the cell which mediated by a acceptor probably. Also may cause with the oxygen free radicals which induce the cell membrane pathologic damage. The RA occurrence rate have relation with the time of coronary artery being obstructd . The general 30 minutes being obstructed, RA may reach its peak value . It is reported that SOD can remove the oxygen free radicals then decrease incidence rate of RA. Adenosine can raise the myocardial organization in the SOD activity, and improve the myocardial metabolism, may be one of the mechanism that its anti — RA.(4) This experiment show that A LVSP of the control group and the LV-EDP are obvious higher than those of adenosine group and sham operated . This illustrated that myocardial I/R can damage left ventricular function. But adenosine can activate correspond acceptors to protect the I/ R myocardial, thus improve the left ventricles function of the big I/ R rat.In a word , the I/ R myocardium can aggravate the myocardial injury ,a-denosine can protect the myocardium of I/ R. The physiological effect of adenosine is mostly mediated by adenosine receptors . But the mechanism of post - receptors and signal transduction pathway, is still not quite explicit, needing the further research.Conclusion1. The myocardium can produce a great deal of oxygen free radicals after myocardial ischemia reperfusion. It is the one of the main mechanisms that causes myocardial I/R injury.2. Myocardial ischemia reperfusion can aggravate myocardial injury, which can result in the myocardial cell change of the appearance structure, such as ne-orobiosis, bleeding ,and so on.3. Myocardial ischemia reperfusion often appear the VT or VF, and left ventricles myocardial function decrease.