Cerebrosides of baifuzi, a novel potential blocker of calcium-activated chloride channels in rat pulmonary artery smooth muscle cells

Calcium-activated chloride channels (CaCCs) are crucial regulators of vascular tone by promoting a depolarizing influence on the resting membrane potential of vascular smooth muscle cells. However, the lack of a special blocker of CaCCs has limited the investigation of its functions for long time. Here, we report that CB is a novel potential blocker of ICl(Ca) in rat pulmonary artery smooth muscle cells (PASMC). Cerebrosides (CB) were isolated from Baifuzi which is dried root tuber of the herb Typhonium giganteum Engl used for treatment of stroke in traditional medicine. Using the voltage-clamp technique, sustained Ca2+-activated Cl− current (ICl(Ca)) was evoked by a K+-free pipette solution containing 500 nM Ca2+ which exhibited typical outwardly rectifying and voltage-/time-dependence characterization. Data showed that CB played a distinct inhibitory role in modulating the CaCCs. Moreover, we investigated the kinetic effect of CB on ICl(Ca) and found that it could slow the activation dynamics of the outward current, accelerate the decay of the inward tail current and change the time-dependence characterization. We conclude that CB is a novel potent blocker of CaCCs. The interaction between CB and CaCCs is discussed.