Characteristics and a functional implication of Ca 2+ -activated K + current in mouse aortic endothelial cells

Abstract

We employed the patch-clamp technique to investigate a Ca(2+)-activated K(+) (K(Ca)) current in cultured mouse aortic endothelial cells (MAECs). In the whole-cell mode, an increase in cytosolic [Ca(2+)] ([Ca(2+)](i)) to 2 micro M activated an outwards current. The [K(+)](o)-dependent change of the reversal potentials agreed well with the predicted Nernstian relation, suggesting that it was a K(Ca) current. The Hill coefficient (4) and EC(50) (740 nM) were obtained from the current/[Ca(2+)](i) relationship. Iberiotoxin (50 nM) or apamin (200 nM) failed to inhibit the current, whereas TEA (10 mM) suppressed the current to 73.6+/-1.6% of control ( n=9). The intermediate-conductance, Ca(2+)-activated K(+) (IK(Ca)) channel blockers charybdotoxin (50 nM), clotrimazole (10 micro M) and econazole (10 micro M) inhibited the K(Ca) current to 10.5+/-1.3% ( n=6), 16.6+/-3.1% ( n=6), and 19.3+/-2.5% ( n=5) of control, respectively. The IK(Ca) channel openers chlorzoxazone, zoxazolamine and 1-ethyl-2-benz-imidazolinone and the Ca(2+)-activated Cl(-) channel blocker niflumic acid activated the K(Ca) current. In inside-out patches, the single-channel conductance was 17.7 pS in symmetrical K(+) solutions. RT-PCR analysis showed transcripts of the murine IK1 channel (mIK1) in MAECs. The IK(Ca) channel blockers inhibited the ATP-induced [Ca(2+)](i) increase in MAECs and the endothelium-dependent relaxation of mouse aortic rings. In addition, the IK(Ca) channel openers augmented ATP-induced [Ca(2+)](i) increase in MAECs and evoked endothelium-dependent relaxation of mouse aorta. These results suggest that an mIK1-like channel mediates the native IK(Ca) current in MAECs and may contribute to endothelium-dependent relaxation by modulating MAEC [Ca(2+)](i).

Small- and intermediate-conductance Ca2+-activated K+ channels directly control agonist-evoked nitric oxide synthesis in human vascular endothelial cells

“…1). 1 Collectively, these data are consistent with the rather lowaffinity block by external TEA of both native and recombinant IK Ca channels (IC 50 value: 8 -10 mmol/l) (2,27,35) along with the SK Ca 2 and SK Ca 3 channel isoforms detected in the vascular endothelium (IC 50 values: ϳ3 and ϳ9 mmol/l, respectively) (4,43). Similar to TEA, we also observed that evoked NO production was unaltered in the presence of 50 mol/l BaCl 2 and 100 mol/l ouabain, which block inwardly rectifying K ϩ (Kir) channels (23) and Na ϩ -K ϩ -ATPase (29), respectively (Fig.…”

Blockage of intermediate-conductance-Ca2+-activated K+ channels inhibits progression of human endometrial cancer

“…As shown in Figure 2a, clotrimazole, an inhibitor of IKCa1 channels (Wang et al, 2003;Ahn et al, 2004;Mork et al, 2005), significantly decreased HEC-1-A cell numbers, as manifested by the right shift of the growth curve. Further, HEC-1-A cell proliferation was suppressed by clotrimazole in a dose-dependent manner (Figure 2b).…”

A mathematical model of plasma membrane electrophysiology and calcium dynamics in vascular endothelial cells

“…Equations A1-A3 were fitted to rat mesenteric EC Kir currentvoltage (I-V) data in the Ϫ100 to ϩ40 mV range ( Fig. 2A, solid (9,10), mouse aortic endothelial cells (MAECs) (2), and Xenopus oocytes (81). Whole cell I-V experimental data (10) were rescaled using capacitance values from source cells and rat mesenteric ECs (assumed to be 14 pF) and fitted using the linear K Ca current equations (Fig.…”