The Study Of Ang1-7 On Sodium Current In Hypertrophic Myocardium

Part ?: The intervention of Ang1-7 on cardiac hypertrophy and CX43Objective To observe and compare the differences in the expression of CX43/PS368 in the left ventricular muscle tissues and the changes of Ang1-7 after intervention between the WKY and SHR placebo groups,and to investigate the effect of Ang1-7 on the hypertrophic myocardial tissues.Methods 16-week-old WKY was selected as the normal blood pressure group and 16-week-old SHR as the hypertension group,and SHR was random Ly divided into 2 groups: 5 in the WKY control group,5 in the SHR+NS placebo group,5 in the SHR+ Ang1-7 experimental group.Before intervention,the systolic blood pressure of the tail artery of the 3 groups of rats was measured and recorded by caudal sleeve method.Animal intervention: no intervention was performed in the WKY group,the placebo group was subcutaneously implanted with a micro osmotic pump to pump normal saline,and the experimental group was subcutaneously implanted with a micro osmotic pump to pump Ang1-7 for intervention.After that,thoracotomy and coring were performed under isoflurane inhalation anesthesia,and the intermediate tissues of the left ventricle(if not specified in this paper,both myocardial tissue and myocardial cells refer to the left ventricular myocardium)were left as the experimental staining part,fixed with paraformaldehyde for 6-8 hours,and sections were embedded in paraffin.Changes in myocardial hypertrophic and fibrosis degree were observed with HE and Masson staining,respectively,and differences in distribution of CX43/PS368 were observed with immunohistochemical staining.A small part of the left heart was stored in the-80? refrigerator,and Western Blot was used to detect the differences of CX43/PS368 expression.Based on the above results,the effects of Ang1-7 on SHR myocardial hypertrophy and degree of fibrosis and CX43/PS368 expression were analyzed.Results The results of systolic blood pressure in the tail artery of rats in the three groups showed that,compared with the WKY group,blood pressure in the SHR+NS group and SHR+A group were significantly increased before intervention(p<0.01),and there was no statistical difference in blood pressure between the SHR+NS group and SHR+A group(p>0.05).After intervention,compared with WKY,blood pressure in both SHR+NS group and SHR+A group was significantly increased(p<0.01),but compared with SHR+NS group,blood pressure in SHR+A group was significantly decreased(p<0.01).HE staining results showed that the cardiomyocytes in the WKY group were in orderly arrangement and had clear tissue structure,the cardiomyocytes in the SHR+NS group were in disordered arrangement and had unclear tissue structure,and the SHR+A group was in between.Masson staining showed that WKY blue dyeing was not obvious,SHR+NS group was obvious,and SHR+ Ang1-7 group was in between.Compared with WKY,the expression of CX43/PS368 in SHR+NS group by Western Blot significantly decreased(p<0.05),and SHR+A significantly increased(p<0.05)compared with SHR+NS group,but still significantly less than WKY group(p<0.05).Immunohistochemical results showed that compared with WKY,CX43/PS368 in SHR+NS group was significantly decreased(p<0.05),and SHR+A was significantly increased (p<0.05)compared with SHR+NS group,but still significantly lower than WKY group(p<0.05).Conclusion There were significant differences in blood pressure,myocardial hypertrophy and degree of fibrosis between WKY and SHR,as well as differences in the expression and distribution of CX43/PS368,which were significantly reduced after Ang1-7 intervention.This study laid a structural and electrophysiological foundation for the next step observation of Ang1-7 on SHR ventricular sodium current.Part ?: Isolation of rat cardiomyocytes and recording of sodium currentObjective To compare the quantity and quality of myocardial cells isolated from SD,WKY and SHR by modified Langendorff aortic retrograde perfusion combined with enzymatic digestion.The difference of sodium current between hypertrophic myocardium and normal myocardium was compared,and the changes of sodium current in hypertrophic myocardium after Ang1-7 intervention were studied,so as to explore the application value of Ang1-7 in electrophysiology of hypertrophic myocardium.Methods Rats were divided into groups and intervention as the first part.Preliminary experiments were conducted to compare the quantity and quality of myocardial cells isolated from SD,WKY and SHR by modified Langendorff aortic retrograde perfusion combined with enzymatic digestion in 2 steps.After the intervention,cardiomyocytes from the WKY,SHR placebo group and the experimental group were isolated by modified Langendorff aortic retrograde perfusion combined with enzymatic digestion 2 step method under isoflurane inhalation anesthesia.Patch clamp technique was used to record the capacitance of single myocardial cell membrane,peak sodium current,sodium current activation and i-v curve changes in whole-cell mode.Results Eighty to ninety percent of the long rod cells with clear transverse striations were obtained in the three groups.The peak sodium current in SHR+NS group was significantly higher than that in WKY group(p<0.05),while the peak sodium current in SHR+A group was significantly lower than that in SHR+NS group(p<0.05).Compared with the WKY group,the membrane capacitance value of the SHR+NS group and the SHR+A group both increased significantly(p<0.05).Compared with the SHR+NS group,the film capacitance value of the SHR+A group was significantly reduced(p<0.05).However,there was no significant difference in current density between the three groups in pairwise comparison(p>0.05).Conclusion There was no difference in the survival rate of myocardial rod cells in the 3 groups isolated by modified Langendorff aortic retrograde perfusion combined with enzyme digestion.Subcutaneous microosmotic pumping of Ang1-7 can affect the peak of sodium activation current and the size of membrane capacitance of SHR cardiomyocytes.