Study of the interaction of sulfur dioxide derivative with cardiac sodium channel

The effects of sulfur dioxide (SO2) derivatives (bisulfite and sulfite, 1:3 M/M) on voltage-dependent sodium channel in isolated rat ventricular myocyte were studied using the whole cell patch-clamp technique. SO2 derivatives increased sodium current (INa) in a concentration-dependent manner. SO2 derivatives at 10 μM significantly shifted steady-state inactivation curve of INa to more positive potentials, but did not affect the activation curve. SO2 derivatives markedly shifted the curve of time-dependent recovery of INa from inactivation to the left, and accelerated the recovery of INa. SO2 derivatives also significantly shortened the activation and inactivation time constants of INa. These results indicated that SO2 derivatives produced concentration-dependent stimulation of cardiac sodium channels, which due mainly to the interaction of the drug with sodium channels in the inactivated state.