Redox modulation of L-type calcium channels in ferret ventricular myocytes - Dual mechanism regulation by nitric oxide and S-nitrosothiols

The effects of NO-related activity and cellular thiol redox state on basal L-type calcium current, I-Ca,I-L, in ferret right ventricular myocytes were studied using the patch clamp technique. SIN-1, which generates both NO . and O-2(-), either inhibited or stimulated I-Ca,I-L. In the presence of superoxide dismutase only inhibition was seen. 8-Br-cGMP also inhibited I-Ca,I-L, suggesting that the NO inhibition is cGMP-dependent. On the other hand, S-nitrosothiols (RSNOs), which donate NO+, stimulated I-Ca,I-L. RSNO effects were not dependent upon cell permeability , modulation of SR Ca2+ release, activation of kinases, inhibition of phosphatases, or alterations in cGMP levels. Similar activation of I-Ca,I-L by thiol oxidants, and reversal by thiol reductants, identifies an allosteric thiol-containing ''redox switch'' on the L-type calcium channel subunit complex by which NO ./O-2(-) and NO+ transfer can exert effects opposite to those produced by NO .. In sum, our results suggest that: (a) both indirect (cGMP-dependent) and direct (S-nitrosylation/oxidation) regulation of ventricular I-Ca,I-L and (b) sarcolemma thiol redox state may be an important determinant of I-Ca,I-L activity.