| Objective To observe the effect of acute myocardial infarction and atrialtachyarrhythmia （ATS）on myocardium plasma B-type natriuretic peptide (BNP)of rabbit,to analyze the change of BNP, to investigate the relationship and mechanismbetween them.Methods32expermental rabbits were divided randomly into4groups, largemyocardial infarction group, less extensive myocardial infarction group, arrhythmiaalone group, control group.(1) Large myocardial infarction group: their leftcoronary artery were ligated to cause myocardial infarction. In case of no arrhythmia,they were stimulated in10seconds by the Electrophysiological stimulator, applied inS1S1method, with the higher frequency than the former stimulation frequency of20beats per min（bpm）, at the surface of atrium as well as ventricle for each of10seconds,to induce arrhythmia, and ECG were recorded timely.(2) Less extensivemyocardial infarction group: the position of coronary artery ligation were changed to1/3of middle-upper left circumflex branch of coronary artery. with the ligationmethod and process as the former group.(3)Arrhythmia alone group: In this group,they were stimulated by the electrical stimulator on the heart surface for only5minutes, on atrial by the frequency of600bpm, on ventricular by the frequency of400bpm, with the ligation position, method and process as the former group.(4)Control group: Ligation of the coronary or electrical stimulation in this group had notbeen, and the rest dealing with the former group.The levels of serum BNP andcreatine kinase isoenzyme (CK-MB)at the time points, which were before theexperiment and after2h,4h,6h,8h to the experiment,were detected by ELISA. TheBNP expression in different parts of the heart was detected with theImmunohistochemical method (IHC). Results (1) There was no significant difference (P>0.05) among the levels of BNPand CK-MB of each group before the occurrence of AMI myocardial infarction.(2)There was obvious rise of the serum BNP and CK-MB levels in each group, afterligation of coronary arteries or arrhythmias was induced, which is in direct proportionto time of infarction.. The levels of the group with large infarction increased the mostobvious group, followed by the group with less extensive infarction, the group witharrhythmia alone ranks third, no significant increase in the control group. Theintergroup difference was significant (P<0.01).(3) In each group, the positiveexpression of BNP in myocardial sections were different significantly (P<0.01). Thegroup with large infarction and the group with less extensive infarction were found alarge number of BNP expression and deeply stained in the nuclei and cytoplasm ofventricular slices. The BNP of the control group had only a small amount ofexpression or no expression in the nucleus and cytoplasm. Each BNP positiveexpression level: The group with large infarction> The group with less extensiveinfarction> The group with arrhythmia alone> control group, the difference wassignificant among the groups (P<0.01). The quantities of BNP expression in atrialtissue were more than the ventricular tissue of The group with arrhythmia alone, andthe difference was significant (P<0.01). And there were positive correlation betweenatrial arrhythmia incidence rate and the expression of BNP.Conclusion The result of this study shows that there is a close relationship betweenthe occurrence of atrial tachyarrhythmia and the BNP level in the case of acutemyocardial infarction of rabbits. The BNP level was higher, the rate of atrialtachyarrhythmia was higher.And The quantities of BNP expression in atrial tissuewere more than the ventricular tissue of the group with arrhythmia alone,which showsthe compounding and secreting of the BNP in atrial tissue were more than the othertissue. By the analysis on the BNP level, the occurrence of acute myocardialinfarction accompanying atrial tachyarrhythmia can be predicted. |
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