Gao Y, Vanhoutte P M
Department of Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota 55905.
J Appl Physiol (1985). 1988 Dec;65(6):2400-5. doi: 10.1152/jappl.1988.65.6.2400.
Experiments were designed to determine whether the airway epithelium affects the membrane potential of the underlying smooth muscle. The effect of epithelium removal (by gentle rubbing) on the responsiveness of isolated canine bronchi was studied. Simultaneous recordings of mechanical and electrical activity were made in paired circumferential strips (with and without epithelium) of third-order bronchi. Changes in tension were recorded with a force transducer, and changes in membrane potential were measured with a microelectrode. The cell membrane potential and resting tension of the bronchial smooth muscle were stable over a 150-min period and were not affected by removal of the epithelium. In the presence of antagonists at muscarinic and adrenergic receptors, the resting tension and membrane potential were comparable in preparations with and without epithelium. By contrast, the anticholinesterase, echothiophate, caused depolarization in bronchi without epithelium. Exposure to high potassium induced similar levels of depolarization and contraction in tissues with and without epithelium. No significant differences in threshold for depolarization or for mechanical activation in the membrane potential-tension relationship were noted in the presence or absence of epithelium. In the presence of echothiophate, removal of the epithelium augmented the contraction of the bronchi to acetylcholine; the depolarization of the cell membrane induced by the cholinergic transmitter was significantly larger than in control tissues, even when matched contractions were compared. These observations indicate that the respiratory epithelium generates an inhibitory substance that dampens depolarization and contraction of bronchial smooth muscle caused by acetylcholine.
设计实验以确定气道上皮是否会影响其下方平滑肌的膜电位。研究了去除上皮（通过轻柔摩擦）对离体犬支气管反应性的影响。在三级支气管的成对环形条带（有上皮和无上皮）中同时记录机械和电活动。用测力传感器记录张力变化，用微电极测量膜电位变化。支气管平滑肌的细胞膜电位和静息张力在150分钟内保持稳定，且不受上皮去除的影响。在存在毒蕈碱和肾上腺素能受体拮抗剂的情况下，有上皮和无上皮的标本中静息张力和膜电位相当。相比之下，抗胆碱酯酶依可碘酯会使无上皮的支气管发生去极化。暴露于高钾会在有上皮和无上皮的组织中诱导相似程度的去极化和收缩。在有或无上皮的情况下，膜电位 - 张力关系中去极化阈值或机械激活阈值均未观察到显著差异。在存在依可碘酯的情况下，去除上皮会增强支气管对乙酰胆碱的收缩反应；即使在比较匹配收缩时，胆碱能递质诱导的细胞膜去极化也明显大于对照组织。这些观察结果表明，呼吸道上皮会产生一种抑制物质，该物质可抑制乙酰胆碱引起的支气管平滑肌去极化和收缩。
