Diversity of voltage-dependent K+ channels in human pulmonary artery smooth muscle cells

plays an important role in excitation-contraction coupling in the pulmonary vasculature, is regulated by transmembrane ion flux in pulmonary artery smooth muscle cells (PASMC). This study exam-ined the heterogeneous nature of native voltage-dependent K chan-nels in human PASMC. Both voltage-gated K (KV) currents and Ca2-activated K (KCa) currents were observed and characterized. In cell-attached patches of PASMC bathed in Ca2-containing solu-tions, depolarization elicited a wide range of K unitary conductances (6–290 pS). When cells were dialyzed with Ca2-free and K-containing solutions, depolarization elicited four components of KV currents in PASMC based on the kinetics of current activation and inactivation. Using RT-PCR, we detected transcripts of 1) 22 K