The Role Of Clc-3 Chloride Channel Protein In Adrenoceptor Activation-induced Myocardial Hypertrophy

Objective: To investigate the role of Cl C-3 chloride channel protein in adrenoceptor activation-induced myocardial hypertrophy.Methods:(1) A mouse model of myocardial hypertrophy was established by intraperitoneal injection of adrenergic receptor agonists.(2) Interventricular septum, ventricular wall thickness, and the mouse heart index(HW/BW) were assessed by small animal echocardiography, then achieved mice cardiac index(HW/BW). The degree of cardiac hypertrophy was determined by cardiac tissue HE staining combined with echocardiography.(3) The expression of Cl C-3 protein in cardiac tissue was detected by immunohistochemistry.(4) Neonatal rat cardiomyocytes were cultured by trypsin digestion and spontanous beating of cardiomyocytes was recorded by video system.(5) Real-time PCR technology was used to measure the expression of atrial natriuretic factor(ANF) and ClC-3 m RNA in cardiomyocyte and the heart tissue.(6) Western blot was used to detect Cl C-3 protein of cardiomyocyte and the heart tissue.(7) The volume of cells was measured by the Countstar automated cell counter.Results:(1) The mouse model of myocardial hypertrophy was successfully established by intraperitoneal injection of adrenergic receptor agonist isoproterenol( ISO) or norepinephrine(NE)The Interventricular septum, left ventricular posterior and heartindex(HW/BW) revealed a significant increase in the chamber cavity. Compared with control groups myocardial structure in ISO and NE treated groups was looser, the collagen fiber content increased, myocardial fibers were cruder, the myofibril cross-sectional area increased obviously,and the nuclei aggregated and swelled.(2) Compared with control groups the expression of ANF in mice given with ISO or NE was increased. While the expression of Cl C-3 m RNA was obviously reduced. Results from immunohistochemistry and western blot also showed that Cl C-3 chloride channel protein expression was significantly decreased.(3) β adrenoceptor antagonist propranolol(Pro) retarded the cardiac hypertrophy induced by ISO. Compared with control groups, heart index(HW/BM) declined significantly. Compared with NE treatment groups, heart index of mice treated with α adrenoceptor antagonist phentolamine(Phe) has a tendency of decrease.(4) Compared with model groups, the expression of ANF decreased obviously in the Pro groups and Phe groups. The expression of Cl C-3 restored to near normal level.(5) Both ISO and NE increased the cell volume of neonatal rat cardiomyocytes and H9c2 myocardial cells.(6) Compared with control groups the expression of ANF in myocytes treated with ISO or NE was increased. The expression of Cl C-3 m RNA and protein were reduced.Conclusion:Adrenergic receptors activation induced cardiac hypertrophy and down-regulated the expression of Cl C-3.