Bonnet Sébastien, Savineau Jean-Pierre, Barillot Wilfrid, Dubuis Eric, Vandier Christophe, Bonnet Pierre
INSERM (EMI 0356), Université Bordeaux 2, 146 rue Léo-Saignat, 33076, Bordeaux, France.
Cardiovasc Res. 2003 Nov 1;60(2):326-36. doi: 10.1016/s0008-6363(03)00527-3.
Clinically, the effect of chronic hypoxia (CH) in the pulmonary circulation alternates between phases of pulmonary artery hypertension (CH-PAHT) and normoxic normotensive remission (N-RE). Little information is available on the role of calcium-sensitive potassium channels (BK(Ca)) in both CH-PAHT and N-RE phases. In the present study, we investigated the effects of both CH and N-RE on BK(Ca) channels activity and their consequences on hypoxic pulmonary vasoconstriction (HPV).
Using isolated ring preparation, the patch-clamp technique, RT-PCR and Western immunoblotting, we examined the role of the BK(Ca) channel in normoxic, CH-PAHT and N-RE rat pulmonary artery smooth muscle cells (PASMCs).
In intrapulmonary arterial rings, acute hypoxia induced contraction in control vessels, relaxation in the N-RE rats, and had no effect in CH-PAHT. The hypoxia-induced relaxation in the N-RE rat pulmonary arteries was abolished by iberiotoxin (IbTx), a specific BK(Ca) blocker. The IbTx-sensitive whole-cell K(Ca) channel current was reduced in CH-PAHT and increased in N-RE rat PASMCs. The BK(Ca) channel conductance and voltage sensitivity were not altered in CH and N-RE rat PASMCs, whereas its calcium sensitivity was decreased and increased in CH and N-RE rat PASMCs, respectively. Results of RT-PCR and Western blot analysis revealed a decrease in the mRNA and protein of the BK(Ca) alpha-subunit in CH, whereas no change at protein level was observed in the N-RE.
In rat PASMCs, CH and N-RE are associated with a down- and up-regulation of BK(Ca) activity, respectively, mainly due to modifications of its Ca(2+) sensitivity. This could explain the acute hypoxic pulmonary constriction and relaxation observed in CH and N-RE rats, respectively.
临床上，慢性缺氧（CH）在肺循环中的作用在肺动脉高压（CH-PAHT）阶段和常氧常压缓解期（N-RE）之间交替变化。关于钙敏感性钾通道（BK(Ca)）在CH-PAHT和N-RE阶段中的作用，目前所知甚少。在本研究中，我们探究了CH和N-RE对BK(Ca)通道活性的影响及其对缺氧性肺血管收缩（HPV）的影响。
采用离体血管环制备、膜片钳技术、逆转录聚合酶链反应（RT-PCR）和蛋白质免疫印迹法，我们研究了BK(Ca)通道在常氧、CH-PAHT和N-RE大鼠肺动脉平滑肌细胞（PASMCs）中的作用。
在肺内动脉环中，急性缺氧在对照血管中诱导收缩，在N-RE大鼠中诱导舒张，而在CH-PAHT中无作用。特异性BK(Ca)阻滞剂iberiotoxin（IbTx）可消除N-RE大鼠肺动脉中缺氧诱导的舒张。CH-PAHT大鼠PASMCs中IbTx敏感的全细胞钾通道电流降低，而N-RE大鼠PASMCs中该电流增加。CH和N-RE大鼠PASMCs中BK(Ca)通道的电导和电压敏感性未改变，但其钙敏感性在CH大鼠PASMCs中降低，在N-RE大鼠PASMCs中增加。RT-PCR和蛋白质印迹分析结果显示，CH中BK(Ca)α亚基的mRNA和蛋白质减少，而N-RE中蛋白质水平未观察到变化。
在大鼠PASMCs中，CH和N-RE分别与BK(Ca)活性的下调和上调相关，主要是由于其Ca(2+)敏感性的改变。这可以分别解释CH和N-RE大鼠中观察到的急性缺氧性肺收缩和舒张。
