Functional characterization of voltage-gated K⁺ channels in mouse pulmonary artery smooth muscle cells

Abstract

June 20, 2007; doi:10.1152/ajpcell.00101.2007.-Mice are useful animal models to study pathogenic mechanisms involved in pulmonary vascular disease. Altered expression and function of voltage-gated K ϩ (KV) channels in pulmonary artery smooth muscle cells (PASMCs) have been implicated in the development of pulmonary arterial hypertension. KV currents (IK(V)) in mouse PASMCs have not been comprehensively characterized. The main focus of this study was to determine the biophysical and pharmacological properties of IK(V) in freshly dissociated mouse PASMCs with the patch-clamp technique. Three distinct whole cell IK(V) were identified based on the kinetics of activation and inactivation: rapidly activating and noninactivating currents (in 58% of the cells tested), rapidly activating and slowly inactivating currents (23%), and slowly activating and noninactivating currents (17%). Of the cells that demonstrated the rapidly activating noninactivating current, 69% showed IK(V) inhibition with 4-aminopyridine (4-AP), while 31% were unaffected. Whole cell IK(V) were very sensitive to tetraethylammonium (TEA), as 1 mM TEA decreased the current amplitude by 32% while it took 10 mM 4-AP to decrease I K(V) by a similar amount (37%). Contribution of Ca 2ϩ -activated K ϩ (KCa) channels to whole cell IK(V) was minimal, as neither pharmacological inhibition with charybdotoxin or iberiotoxin nor perfusion with Ca 2ϩ -free solution had an effect on the whole cell I K(V). Steady-state activation and inactivation curves revealed a window K ϩ current between Ϫ40 and Ϫ10 mV with a peak at Ϫ31.5 mV. Single-channel recordings revealed large-, intermediate-, and smallamplitude currents, with an averaged slope conductance of 119.4 Ϯ 2.7, 79.8 Ϯ 2.8, 46.0 Ϯ 2.2, and 23.6 Ϯ 0.6 pS, respectively. These studies provide detailed electrophysiological and pharmacological profiles of the native K V currents in mouse PASMCs.

Perinatal hypoxia triggers alterations in K+channels of adult pulmonary artery smooth muscle cells

“…This demonstrates the contribution of K V channels but not BK Ca channels to this outward current. Similar observations were recently reported in adult mice of a different strain (23). Western blotting analysis of K V 1.5 ␣-subunit and BK Ca ␣-subunit expression showed that both proteins were present in the main PA of adult mice born in normoxia, suggesting that, in basal conditions, K Ca channels are present but not active.…”

Hypoxia sensitivity of a voltage-gated potassium current in porcine intrapulmonary vein smooth muscle cells

“…The biophysical features of this current are consistent with previously reported voltage-gated, Ca 2ϩ -independent K ϩ currents with rapid rates of activation and steady-state inactivation in pulmonary smooth muscle (32). The rapid rate of activation of I KH was comparable to observations made in rabbit portal vein smooth muscle (time to peak ϳ20 ms) (4) but slower than the ultrafast activating Fig.…”

Functional characterization of voltage-dependent Ca2+ channels in mouse pulmonary arterial smooth muscle cells: divergent effect of ROS

“…Freshly dissociated PASMC from mouse PA isolated from second-to third-order intrapulmonary arterial branches (100-to 400-m diameters) were used to measure the electrophysiological properties of VDCC. As previously reported (28), the freshly dissociated mouse PASMC from intrapulmonary arteries were oblong, unlike the long spindle-shaped cells isolated from other species ( Fig. 2A).…”