cAMP-dependent phosphorylation modulates voltage gating in an endothelial Cl- channel

Using the patch clamp technique in the cell-attached, inside-out, and outside-out configurations, we have identified a voltage-gated outwardly rectifying, large conductance (400 pS) Cl- channel in patches from the surface membrane of a cultured monolayer of bovine aortic endothelial cells. The channel is activated in cell-attached patches with 1 microM isoproterenol or 1 mM dibutyryladenosine 3',5'-cyclic monophosphate. In excised inside-out patches the voltage dependence of this channel could be fitted by a Boltzmann distribution with a half-activation voltage (V1/2) at 0 mV. Adenosine 3',5'-cyclic monophosphate (cAMP)-dependent phosphorylation induces a shift of -50 mV in V1/2. Alkaline phosphatases restores the voltage dependence of the channel to control values. The channel is reversibly blocked by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid. The half-inhibitory concentration was approximately 70 microM. Our results suggest that beta-adrenergic stimulation (which increases intracellular cAMP levels in this endothelium) may increase Cl- permeability at the cell resting potential by shifting the voltage dependence of this channel.