AIM:To investigate the effects of autoantibodies against β_1-adrenoceptor in hepatitis virus myocarditis on action potential and L-type Ca^(2+) currents. METHODS:Fifteen samples of autoantibodies against β_1- adreno...AIM:To investigate the effects of autoantibodies against β_1-adrenoceptor in hepatitis virus myocarditis on action potential and L-type Ca^(2+) currents. METHODS:Fifteen samples of autoantibodies against β_1- adrenoceptor positive sera of patients with hepatitis virus myocarditis were obtained and IgGs were purified by octanoic acid extraction.Binding of autoantibodies against β_1- adrenoceptor to guinea pig cardiac myocytes was examined by immunofluorescence.Using the patch clamp technique, the effects on the action potential and I_(ca-L) of guinea pig cardiac myocytes caused by autoantibodies against β_1-adrenoceptor in the absence and presence of metoprolol were investigated. Cell toxicity was examined by observing cell morphology and permeability of cardiac myocytes to trypan blue. RESULTS:The specific binding of autoantibodies against β_1-adrenoceptor to guinea pig cardiomyocytes was observed. Autoantibodies against β_1-adrenoceptor diluted at 1:80 prolonged APO_(20),APD_(50)and APD_(90) by 39.2%,29.1% and 15.2% respectively,and only by 7.2%,5.3% and 4.1% correspondingly in the presence of 1 μmol/L metoprolol. Autoantibodies against β_1-adrenoceptor diluted at 1:80, 1:100 and 1:120 significantly increased the I_(ca-l) peak current amplitude at 0 mV by 55.87±4.39%,46.33±5.01% and 29.29±4.97% in a concentration-dependent manner.In contrast,after blocking of β_1-adrenoceptors (1 μmol/L metoprolol),autoantibodies against β_1-adrenoceptor diluted at 1:80 induced a slight increase of I_(ca-L) peak amplitude only by 6.81±1.61%.A large number of cardiac myocytes exposed to high concentrations of autoantibodies against β_1- adrenoceptor (1:80 and 1:100) were turned into rounded cells highly permeable to trypan blue. CONCLUSION:Autoantibodies against β_1-adrenoceptor may result in arrhythmias and/or impairment of myocardiums in HVM,which would be mediated by the enhancement of I_(ca-L.展开更多
The hyperpolarization-activated current (If) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart, therefore...The hyperpolarization-activated current (If) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart, therefore we studied developmental changes in functional expression and β-adrenergic regulation of Iy in embryonic mouse heart. The expression of If is high in early developmental stage (EDS) (10.5 d after coitus) ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytes and even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating that these cells of the EDS embryonic heart have some properties of pacemaker cells.β-adrenergic agonist isoproterenol (ISO) stimulates If in LDS but not in EDS cardiomyocytes, indicating that the β-adrenergic regulation of If is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase) and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase the amplitude of If in EDS cells, indicating that adenylate cyclase and cAMP function fairly well at early stage of development. Furthermore, the results demonstrate that If is modulated by phosphorylation via cAMP dependent PKA both in EDS and LDS cells.展开更多
基金Supported by the National Natural Science Foundation of China,NO.39970306
文摘AIM:To investigate the effects of autoantibodies against β_1-adrenoceptor in hepatitis virus myocarditis on action potential and L-type Ca^(2+) currents. METHODS:Fifteen samples of autoantibodies against β_1- adrenoceptor positive sera of patients with hepatitis virus myocarditis were obtained and IgGs were purified by octanoic acid extraction.Binding of autoantibodies against β_1- adrenoceptor to guinea pig cardiac myocytes was examined by immunofluorescence.Using the patch clamp technique, the effects on the action potential and I_(ca-L) of guinea pig cardiac myocytes caused by autoantibodies against β_1-adrenoceptor in the absence and presence of metoprolol were investigated. Cell toxicity was examined by observing cell morphology and permeability of cardiac myocytes to trypan blue. RESULTS:The specific binding of autoantibodies against β_1-adrenoceptor to guinea pig cardiomyocytes was observed. Autoantibodies against β_1-adrenoceptor diluted at 1:80 prolonged APO_(20),APD_(50)and APD_(90) by 39.2%,29.1% and 15.2% respectively,and only by 7.2%,5.3% and 4.1% correspondingly in the presence of 1 μmol/L metoprolol. Autoantibodies against β_1-adrenoceptor diluted at 1:80, 1:100 and 1:120 significantly increased the I_(ca-l) peak current amplitude at 0 mV by 55.87±4.39%,46.33±5.01% and 29.29±4.97% in a concentration-dependent manner.In contrast,after blocking of β_1-adrenoceptors (1 μmol/L metoprolol),autoantibodies against β_1-adrenoceptor diluted at 1:80 induced a slight increase of I_(ca-L) peak amplitude only by 6.81±1.61%.A large number of cardiac myocytes exposed to high concentrations of autoantibodies against β_1- adrenoceptor (1:80 and 1:100) were turned into rounded cells highly permeable to trypan blue. CONCLUSION:Autoantibodies against β_1-adrenoceptor may result in arrhythmias and/or impairment of myocardiums in HVM,which would be mediated by the enhancement of I_(ca-L.
基金supported by the National Natural Science Foundation of China,No.30070279
文摘The hyperpolarization-activated current (If) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart, therefore we studied developmental changes in functional expression and β-adrenergic regulation of Iy in embryonic mouse heart. The expression of If is high in early developmental stage (EDS) (10.5 d after coitus) ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytes and even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating that these cells of the EDS embryonic heart have some properties of pacemaker cells.β-adrenergic agonist isoproterenol (ISO) stimulates If in LDS but not in EDS cardiomyocytes, indicating that the β-adrenergic regulation of If is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase) and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase the amplitude of If in EDS cells, indicating that adenylate cyclase and cAMP function fairly well at early stage of development. Furthermore, the results demonstrate that If is modulated by phosphorylation via cAMP dependent PKA both in EDS and LDS cells.
