Modulation of L-type calcium current in rat cardiac myocytes by sulfur dioxide derivatives

The effects of sulfur dioxide (SO2) derivatives (bisulfite and sulfite, 1:3 M/M) on voltage-dependent L-type calcium current (ICa,L) in isolated rat ventricular myocytes were studied using the whole cell patch-clamp technique. SO2 derivatives increased ICa,L in a concentration-dependent manner. SO2 derivatives shifted both the steady-state activation and the inactivation curves of ICa,L to more positive potentials, the effect on the latter being more pronounced. SO2 derivatives markedly accelerated the recovery of ICa,L from inactivation. SO2 derivatives also significantly shortened the fast and slow time constants of inactivation. These results suggested that SO2 inhalation might cause cardiac myocyte injury through increasing intracellular calcium via voltage-gated calcium channels.