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Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of California, San Diego, California 92103
Submitted 9 December 2003 ; accepted in final form 19 March 2004
Electrical excitability, which 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 examined the heterogeneous nature of native voltage-dependent K+ channels 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 solutions, depolarization elicited a wide range of K+ unitary conductances (6290 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 KV channel
-subunits (KV1.11.7, KV1.10, KV2.1, KV3.1, KV3.33.4, KV4.14.2, KV5.1, KV 6.16.3, KV9.1, KV9.3, KV10.1, and KV11.1), 2) three KV channel
-subunits (KV
13), 3) four KCa channel
-subunits (Slo-
1 and SK2SK4), and 4) four KCa channel
-subunits (KCa
14). Our results show that human PASMC exhibit a variety of voltage-dependent K+ currents with variable kinetics and conductances, which may result from various unique combinations of
- and
-subunits forming the native channels. Functional expression of these channels plays a critical role in the regulation of membrane potential, cytoplasmic Ca2+, and pulmonary vasomotor tone.
membrane potential; calcium; proliferation; heterogeneity; calcium-activated potassium channel
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