ABSTRACT
AIM: To investigate the effect of hypoxia on persistent sodium current (I_Nap ) in single ventricular myocyte isolated from acute myocardial infarction (AMI) heart of rats and to study the mechanisms of cardiac arrhythmias that occur after AMI. METHODS: AMI model was induced by ligating the left anterior descending coronary artery in rats. The whole-cell patch clamp technique was used to record the current in epicardial myocytes in infarcted region from rats at 3 week after AMI. RESULTS: In normoxic conditions, the current density of I_ Nap in cardiomyocytes of fake operation (FO) and AMI hearts was 0.144?0.022 pA/pF (n=9), 0.121?0.013 pA/pF (n=9,P
ABSTRACT
AIM: To observe the changes of Ca-L current (ICa-L) and to investigate the mechanism of salvia miltiorrhizae (SM) for eliminating Ca~2+ overloaded in cells during acute hypoxia/reoxygenation. METHODS: The whole cell patch clamp technique was applied to study the changes of ICa-L. Different concentrations (32, 320, ~3 200 mg/L) of SM were added to the ventricular myocytes isolated from guinea pigs by enzyme digestion. RESULTS: SM (32, 320, ~3 200 mg/L) decreased the amplitude of ICa-L in a concentration-dependent manner regardless of these cells were under normoxia, hypoxia or reoxygenation. Furthermore, SM at low concentration (32 mg/L) was more effective to hypoxia or reoxygenation-treated cells than that to the cells under normoxia condition. CONCLUSION: These results indicate that SM effectively decreases the abnormal raised amplitude of ICa-L in ventricular myocytes under hypoxia or reoxygenation conditions, preventing Ca~2+ overloaded in the cells. [
ABSTRACT
AIM: To study the effects of taurine on ATP sensitive potassium channel (IK_~-ATP ) during hypoxia in single ventricular myocyte. METHODS: The model of myocardial hypoxia was induced by unmixed and saturated nitrogen. IK_~-ATP activities were measured by whole-cell patch clamp recording. RESULTS: Activities of IK_~-ATP in the cell membrane of hypoxia ventricular myocyte significantly increased, compared to that in the normal. Extracellular injection of taurine (5,10,20 mmol/L) inhibited the increase in the IK_~-ATP activity in the hypoxia myocardium in a concentration-depend manner. Injection of taurine also recovered shorten APD during hypoxia. CONCLUSIONS: Taurine produces its cardioprotective effect by inhibiting the activity of IK_~-ATP in the hypoxia cardiomycytes of guinea pig. The results suggest that the depletion of taurine during myocardial hypoxia contributes to the early activation of the K_~ATP channel. [