| Objective The purpose of this subject is to investigate the expression of myocardial connexin 43 via establishing a model of sympathominetic atrial fibrillation,which is in order to explore the potential inner mechanism of occurrence and maintaince in sympathominetic atrial fibrillation.Methods To establish a model of sympathominetic atrial fibrillation.We choosed 15 healthy mongrels,which was divided into 3 groups randomly:1.control group,All of the mongrels' heart were taken out rapidly to establish langerndorff perfusion cardiac model perfused with tyrode's solution in vitro via median sternotomy.The experiment lasted for about 1 hour.2.Rapid atrial pacing group(RAP group),the protocol of perfusion was the same as control group,while during the perfusing time,we used electrophysiological instrument to pace atrial with 800/min,a total of 30 times.3.Isoprenaline + rapid atrial pacing group(ISO+RAP group).The protocol of perfusion was the same as RAP group.The tyrode's solution used to perfuse contained 0.1umol/L isoprenaline.(1)Under the condition of isolated perfusion,we intended to establish a model of sympathomimetic atrial fibrillation via rapid atrial pacing.Atrial effectiverefractory period(AERP)and inducibility of atrial fibrillation were tested in each group.After the experiment was terminated,the atrial tissue was cut and fixed with paraformaldehyde for 24 hours.The expression and distribution of nerve growth factor(NGF)and tyrosine hydroxylase(TH)were detected by immunohistochemistry technology.We observed the influence of sympathominetic effect on the heart of rapid pacing.(2)We cut part of atrial tissue.The total protein level of Cx43 and phosphorylation of Cx43 were determined by Western blotting.The expression level of Cx43 mRNA were detected by Q-PCR.The distribution of atrial myocardial Cx43 were also examined by immunofluorescence.The cell apoptosis was analyzed by TUNNEL staining.Mitochondria structure was observed by electron microscope.The generation of ROS in mitochondria were detected by spectrophotofluorometer.Results(1)No significant changes were found in AERP between control group and RAP group(P > 0.05),while in ISO+RAP group,AERP was significant shortened(P<0.05).Atrial fibrillation could be induced successfully in ISO+RAP group,while in control group and RAP group,there were no atrial fibrillation being induced.Compared with control group,the content and distribution of NGF and TH were significantly higher than control group(P<0.05),while ISO+RAP group was higher than RAP group(P < 0.05).(2)Compared with control group,the content of Cx43 and phosphorylated Cx43 were significantly decreased in RAP and ISO+RAP group,and ISO+RAP group were lower than RAP group(P < 0.05).Compared with control group,the fluorescence intensity of Cx43 was also attenuated and Cx43 were lateralized apparently and the mitochondria morphology were slightly swollen and matrixwas intact in RAP group,while Cx43 were characterized as punctuate distribution and the mitochondria were swollen obviously and part of matrix were transparent in ISO+RAP group.The apoptosis index(AI)and the generation of ROS in mitochondria in ISO+RAP group were significantly higher than RAP group and control group(P<0.05),while RAP group were higher than control group(P<0.05).Conclusion 1.We simulate sympathomimetic active effect via isoproterenol perfusion,which can shorten atrial myocardial action potential.The phenomenon show as the reduction of AERP duration.2.Just rapid atrial pacing can not induce atrial fibrillation during the experimental period,while atrial fibrillation can be induced under sympathomimetic effect.Therefore,we establish sympathomimetic atrial fibrillation model successfully.3.In sympathetic atrial fibrillation,sympathetic may induce remodel and down regulation of Cx43 resulting in occurrence of atrial fibrillation via oxidative stress. |
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