Role of Ca-activated K channel and Na pump in the regulation of airway smmoth muscle tone.

1. 肌肉收缩和舒张反应：将分离的支气管段置于器官腔室中，在存在和不存在K通道阻滞剂和瓦巴因的情况下，测定对乙酰胆碱的收缩反应和对各种支气管扩张剂的舒张反应。对沙丁胺醇、福斯克林和硝普沙的松弛反应被这些药物减弱，而格列本脲和阿帕胺对乙酰胆碱诱导的收缩反应没有影响。因此，ca激活的K通道和Na泵通过去极化膜电位参与气道平滑肌张力的调节。环核苷酸的积累在存在和不存在白藜芦醇和瓦巴因的情况下测定细胞内环核苷酸的浓度。沙丁胺醇和福斯克林增加cAMP含量，硝普苷增加cGMP含量，这些作用不受肉毒杆菌毒素和瓦巴因的影响，说明细胞内cAMP和cGMP直接刺激气道平滑肌细胞钙活化的K通道和Na泵。膜片钳研究：DBcAMP和DBcGMP的加入分别引起单K通道离子电流。因此，这些环核苷酸产生了ca激活的K通道打开和na -K- atp酶激活。

1. Muscle contractile and relaxant responsesIsolated bronchial segments were mounted in organ chambers and the contractile responses to acetylcholine and the relaxant responses to various bronchodilating agents were determined in the presence and absence of K channel blockers and ouabain. Acetylcholine-induced contrction was potentiated by charybdotoxin and ouabain, and the relaxant responses to salbutamol, forskolin and nitroprusside were attenuated by these drugs, whereas glibenclamide and apamin had no effect. Thus, Ca-activated K channel and Na pump play roles in the regulation of airway smooth muscle tone by depolarizing membrane potential.2. Accumulation of cyclic nucleotidesIntracellular cyclic nucleotide concentrations were determined in the presence and absence of charybdotoxin and ouabain. Salbutamol and forskolin increased cAMP conctents and nitroprusside increased cGMP contents, and these effects were not altered by charybdotoxin and ouabain, indicating that intracellular cAMP and cGMP directly stimulate Ca-activated K channel and Na pump in airway smooth muscle cells.3. Patch clamp studiesAddition of DBcAMP and DBcGMP each caused single K channel ion current. Therefore, it was confirmed that these cyclic nucleotides produce Ca-activated K channel opening and Na-K-ATPase activation.