Blocking Effect of Salvianolic Acid A on Calcium Channels in Isolated Rat Ventricular Myocytes

Objective: To study the effect of salvianolic acid A (SAA) on L-type calcium current (I-CaL) in isolated ventricular myocytes of Sprague-Dawley rats. Methods: SAA powder was dissolved in normal Tyrode's solution to reach the concentrations of 1, 10, 100, and 1000 mu mol/L. The traditional whole-cell patch-clamp recording technique was employed to evaluate the effects of SAA on I-CaL in single ventricular myocytes which were prepared by Langendorff perfusion apparatus from Sprague-Dawley rats. Results: SAA (1, 10, 100, and 1000 mu mol/L) inhibited I-CaL peak value by 16.23% +/- 1.3% (n=6, P<0.05), 22.9% +/- 3.6% (n=6, P<0.05), 53.4% +/- 3.0% (n=8, P<0.01), and 62.26% +/- 2.9% (n=6, P<0.01), respectively. SAA reversibly inhibited I-CaL in a dose-dependent manner and with a half-blocking concentration (IC50) of 38.3 mu mol/L. SAA at 100 mu mol/L elevated the I-V curve obviously, and shifted the half-active voltage (V-0.5) from (-15.78 +/- 0.86) mV to (-11.24 +/- 0.77) mV (n=6, P<0.05) and the slope (K) from 5.33 +/- 0.74 to 4.35 +/- 0.74 (n=6, P>0.05). However, it did not alter the shapes of I-V curve, steady-state inactivation curve, or recovery from inactivation curve. Conclusions: SAA inhibited I-CaL in a dose-dependent manner. It shifted the steady-state activation curve to a more positive voltage, which indicated that the drug affected the activated state of calcium channels, and suggested that the Ca2+ antagonistic effect of SAA be beneficial in the treatment of myocardial ischemia reperfusion injury.