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

Abstract

The effects of NO-related activity and cellular thiol redox state on basal L-type calcium current, I(Ca,L) in ferret right ventricular myocytes were studied using the patch clamp technique, SIN-1, which generates both NO and O2, either inhibited or stimulated I(Ca,L). In the presence of superoxide dismutase only inhibition was seen. 8-Br-cGMP also inhibited I(Ca,L), suggesting that the NO inhibition is cGMP-dependent. On the other hand, S-nitrosothiols (RSNOs), which donate NO+, stimulated I(Ca,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,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·/O2 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,L), and (b) sarcolemma thiol redox state may be an important determinant of I(Ca,L) activity.