Correlation Between The Connexin 43 Expression And The Myocardial Ischemia

Acute myocardial ischemia is local anemia of myocardium caused by the coronary atherosclerosis. In general, the cause of acute myocardial ischemia, is also including arteritis, embolism, congenital malformations and functional spasm of coronary artery etc. The characters of coronary heart disease of are ischemia and hypoxia. About 50% of the Sudden cardiac death caused by the coronary atherosclerosis. In case of sudden death caused by coronary heart disease, around 40% and 30% patients died 15 min and 15min-2h after myocardium ischemia respectively. There is quite a few morphological changes be seen by routine histopathological study, which being difficulty for diagnosis of early myocardial ischemia. To search some sensitive diagnostic criteria is urgently required.Myocardical gap juncture composes of six gap-junctional proteins (conexins) responsible for low-resistance electrical coupling between cardiac muscle cell membrane. It is a principal base of myocardial conduction velocity and chemical substance exchanges. Although other connexins exist in mammalian myocardium, the principal connexin isoform of mammalian ventricular myocardium is connexin 43. The pattern of gap-juncture distribution in normal myocardium believed to be one major determinant of the normal uniformly anisotropic pattern of electrical propagation. Anomaly cellular coupling is thought to be the main re-entrant arrhythmogenic factor reducing slowly conduction and one-way block. Anomaly expression and distuibution of Cx43 is the anatomic bases of some ventricular arrhythmia.Mostly, study on the Cx families were on the cardiovascular diaseaes in clinical field. A lot of studies on the relationship between the Cx family and arrhythmia were reported since 1990 followed by the propagations of studies on other organs. Study on sudden death is a very important task in the forensic medicine field, especially sudden deaths caused by coronary atherosclerotic heart disease. Myocardial gap junction might involved in the coronary heartdisease.So far no report about the relationship between the Cx family,respeciallythe Cx43,and the sudden death caused by the coronary heart disease inforensic aspect has been searched in journals published either in foreign countries or in China.Objective To investigate the change of Cx43 expression after the acute myocardial ischemia and to look for a sensitive marker for the diagnosis of early acute myocardial ischemia. Methods (1) Rabbit's left coronary arteries were ligated to establish an experimental animal model of early acute myocardial ischemia at the different intervals elapsed 30min, lh, 2h, 4h and 8h after ligation. HE stain, histochemcial stain such as ICH, TEM and IEM as well as image anaylsis and statistic anaylsis were used. (2) Rat's left coronary arteries were ligated as rabbit. Total mRNA was extracted from the left ventricle, amounts of the mRNA of Cx43 and P-actin were measured by reverse transcription-polymerase chain reaction. Amplified products were electrophoresed on an agarose gel, and followed by quantitation analysis by using images analysis and statistic analysis. (3) One case of accidental CO poisoning was studied by using the method of the HE stain, the histochemical stain (HBFP, PTAH and AZAN) and ICH. Results (1) Acute myocardial ischemia in rabbit. No obvious change was found in the myocardium of the interval showed than 8 hours after ligation of left coronary arteries in HE. After 8 hours of myocardial ischemia, a few neutrophil infiltration in myocardium interstitial tissue with cardiac muscle fiber swelling. Normal cardia muscles show yellow color, while the ischemic cardiac muscles show red color in HBFP.The area of red color was strengthen with the prolongation of myocardial ischemia. The distribution of Cx43 gap junctions obviously decreased about 40% area in size at 30 minutes and was disappeared at 480 minutes after ligtion with immunohistochemitry. Mitochondrion swells at 30 min under the TEM. Thirty minutes after ligation GJ displacement has not been seen by IEM.(2) Expression of mRNA of myocardial ischemia in rat as follows: The levels of mRNA decreased along with the prolongation of time elapsed after coronary artery ligation, and disappeared abount 8 hours after ligation. (3) Human myocardium from CO poisoning death: The yellow colorwas shown in ischemic area. Contracted band necrosis was shown by PTAH staining. And mucoid degeneration in myocardium interstitial and Cx43 invisibility. Conclusion: Cx43 might be a sensitive marker for diagnosis in early myocardial ischemia.