Curcumin, a multi-ion channel blocker that preferentially blocks late Na+ current, prevents I/R induced arrhythmias
Description
Ionic currents were recorded in a whole-cell mode of voltage-clamp configuration and the APs were recorded in a current-clamp configuration after the GO seal is implemented in voltage-clamp mode. Voltage protocols, pipette solutions and external solutions were designed to record different ionic currents. Fitmaster (v2x32, HEKA Electronic) and Origin8.0 (Originlab, Northampton, MA, USA) were used for measurement, statistical analysis and graphic fitting. The concentration-response curves fitted with a Hill function of Y=Bmax/[1 + (IC50/D) n], where Y represent percentage inhibition of currents, n is the Hill coefficient, Bmax is the maximum inhibitory percentage of currents and D is the Cur concentration. The steady-state (in)activation curves were fitted with Boltzmann function of Y=1/[1 + exp (Vm – V1/2)/k], where Y represents relative currents (I/Imax) of steady-state inactivation and the relative conductance (G/Gmax) of steady-state activation, respectively.V1/2 is half (in)activation potential, Vm and k are depolarization potential and slope factor, respectively. The conductance (G) was calculated by G=I/(Vm-Vrev) with the data in the I-V curves, where Vrev is the reversal potential. The time-dependent recovery curve was fitted with an Exponential function of Y=1 – exp(-t/τ), where Y represents I/Imax and t is the time intervals between two-pulse. The time constant-τ reflects the rate of recovery from inactivation. The current data was normalized (Current divided by capacitance) and expressed as current density. Data was presented as means± SD. Parametric tests included Student’s t-test and one-way repeated ANOVA, which were followed by the Bonferroni test for two groups and multiple comparisons, respectively. P<0.05 was considered significant.