The Several Harmful Factors Regulate Glycine Receptor α₁ Subunit Expression In The Neonatal Rat Cardiomyocytes

AIMThe myocardial damage usually result from endotoxemia,ischemia/reperfusion, high concentration of glucose or sympathetic nervous system activation excessively.Our recent researches have showed that glycine could protect myocardial cells from the damage induced by lipopolysaccharide or hypoxia/reoxygenation.Further studies suggest that myocardial cells could contain glycine receptor or binding site of glycine,glycine receptor and its subunits in the purified cultured cardiomyocytes were identified by Western blotting.However,no evidence for these harmful factors regulate glycine receptor expression in cardiomyocytes has been found so far.Therefore,We investigated the effects of lipopolysaccharide,hypoxia/reoxygenation, isoproterenol and high concentration of glucose on glycine receptorα₁ subunit expression in the neonatal rat cardiomyocytes.METHODSThe studies were divided into following three parts:Partâ… :Neonatal Sprague-Dawley rats cardiomyocytes were cultured.Then, cultured rat cardiomyocytes were treated with lipopolysaccharide,isoproterenol or high concentration of glucose,respectively,or were exposed to hypoxia/reoxygenation,hypoxia.Subsequently,we examined cell survival rate by CCK-8 reactant.Partâ…¡:Neonatal Sprague-Dawley rats cardiomyocytes were cultured.Then, cultured rat cardiomyocytes were treated with lipopolysaccharide,isoproterenol or high concentration of glucose,respectively,or were exposed to hypoxia/reoxygenation,hypoxia.After that,We applied RT-PCR to monitor the expression of glycine receptorα₁ subunit mRNA. Partâ…¢:Neonatal Sprague-Dawley rats cardiomyocytes were cultured.Then, cultured rat cardiomyocytes were treated with lipopolysaccharide,isoproterenol or high concentration of glucose,respectively,or were exposed to hypoxia/reoxygenation.Subsequently,Western blot was used to detect the expression of glycine receptorα₁ subunit protein.RESULTS1.Compared with the control group,there was no significant difference in the cell survival rate(P＞0.05) in all experiment groups.2.The expression of glycine receptorα₁ subunit mRNA was higher(P＜0.01) in lipopolysaccharide(5,10,20,40,80mg/L) group than that in control group. Moreover,the expression of glycine receptorα₁ subunit protein was higher(P＜0.01) in lipopolysaccharide(20mg/L) group than that in control group.3.Compared with the control group,the expression of glycine receptorα₁ subunit mRNA was increased(P＜0.01) in isoproterenol(20,100,500μmol/L) group. Moreover,the expression of glycine receptorα₁ subunit protein was increased(P＜0.01) in isoproterenol(100μmol/L) group.4.The expression of glycine receptorα₁ subunit mRNA was increased(P＜0.01) in hypoxia/reoxygenation or hypoxia groups compared with the control group. Further,the expression of glycine receptorα₁ subunit protein was also increased (P＜0.01) in hypoxia/reoxygenation group compared with the control group.5.In contrast,the expression of glycine receptorα₁ subunit mRNA was decreased (P＜0.01) in high concentration of glucose(25,50mmol/L) group,and the expression of glycine receptorα₁ subunit protein was also decreased(P＜0.01) in high concentration of glucose(25mmol/L) group.CONCLUSIONLipopolysaccharide,isoproterenol,hpoxia/reoxygenation or hypoxia upregulates the expression of glycine receptorα₁ subunit,but high concentration of glucose downregulates the expression of glycine receptorα₁ subunit in cultured neonatal rat cardiomyocytes.The results indicated that these harmful factors could regulate the function of the glycine receptor through influence the expression of glycine receptorα₁ subunit in cultured neonatal rat cardiomyocytes.