Potassium currents in cultured human pulmonary arterial smooth muscle cells

In this study, using whole cell and single-channel configurations of the patch-clamp technique, we characterized K+ currents (IK) in cultured human pulmonary arterial smooth muscle cells. The net whole cell outward membrane current (IKo) was activated at potentials positive to -60 mV. One component of IKo, IK(dr), was inhibited by 4-aminopyridine (4-AP) and high concentrations of tetraethylammonium (TEA) but was Ca2+ and charybdotoxin (CTX) insensitive. The other component of IKo, IK(Ca), was voltage and Ca2+ dependent and was inhibited by CTX and low concentrations of TEA. Activation of IKo in single-channel recordings was voltage dependent and demonstrated a high-conductance channel (245 +/- 2 pS) that was Ca2+ and CTX sensitive [IK(Ca)] and a low-conductance channel (109 +/- 2 pS) that was inhibited by 4-AP [IK(dr)] but was insensitive to low concentrations of TEA or to an increase in intracellular [Ca2+]. In isolated pulmonary arterial rings, TEA and 4-AP caused an additive increase in arterial tension. To our knowledge these data provide the first characterization of the IK in human pulmonary arterial smooth muscle cells and indicate that IK(Ca) and IK(dr) play an important role in maintaining pulmonary vascular tone. The data confirm previous observations in pulmonary smooth muscle cells of animal models.