Hahn H L, Lang M, Bleicher S, Zwerenz S, Rausch C
Medizinische Poliklinik, Universität Würzburg.
Clin Investig. 1992 Mar-Apr;70(3-4):252-62. doi: 10.1007/BF00184659.
To assess the mechanism of and the role of the epithelium in nicotine-induced bronchoconstriction in vitro, we performed a combined functional and histologic study. Functional study: We suspended tracheal strips or rings from 16 ferrets (1124 +/- 561 g, mean +/- SD) in organ baths. Alternate tracheal strips had their epithelium removed. Dose-response curves to acetylcholine (ACh) and nicotine were established for pairs of tissues with and without epithelium, each pair receiving only one dose of nicotine. Nicotine induced brief muscle contractions not exceeding 25% of the ACh-induced maximum. Contractions were blocked by hexamethonium and 10(-7) M atropine and were abolished or inhibited strongly by tetrodotoxin (TTX), suggesting the involvement of nicotinic neuronal and muscarinic smooth muscle receptors. Removal of the epithelium strongly inhibited contractions at concentrations of nicotine greater than 3 x 10(-5) M which completely removed any dose-response effect. ACh-induced contractions were unchanged, demonstrating smooth muscle integrity. We suggest that the removal of the epithelium attenuates nicotine-induced bronchoconstriction through the removal of nerves running in or close to the epithelium. Histologic study: In tracheae from 15 ferrets (8 male, 7 female), mean weight (+/- SD) 1288 (+/- 470) g, we examined 4 techniques of epithelium removal: (1) gentle scraping with a scalpel blade moved backwards (away from the cutting edge), (2) moving a Q-tip through the unopened tracheal tube without lateral pressure, and (3, 4) stroking the mucosa of opened tracheal segments with a Q-tip, exerting (3) light or (4) moderate pressure. All methods were equally (97%-100%) efficient in removing the epithelium but differed in the amount of damage caused to the basement membrane and/or submucosal tissue. Method (2) caused less damage to the basement membrane than the other methods but still removed almost one-third of it. The study showed that complete removal of the epithelium is at the expense of the submucosa and that a given result of "epithelium removal" is also attributable to removal of the neighboring subepithelial structures.
为了评估体外尼古丁诱导支气管收缩过程中上皮细胞的作用机制，我们进行了功能与组织学相结合的研究。功能研究：我们将16只雪貂（体重1124±561克，均值±标准差）的气管条或气管环悬挂于器官浴槽中。交替的气管条去除其上皮细胞。针对有上皮和无上皮的组织对，建立对乙酰胆碱（ACh）和尼古丁的剂量反应曲线，每组组织对仅接受一剂尼古丁。尼古丁引起短暂的肌肉收缩，不超过ACh诱导的最大收缩的25%。收缩被六甲铵和10⁻⁷M阿托品阻断，并被河豚毒素（TTX）完全消除或强烈抑制，提示烟碱型神经元受体和毒蕈碱型平滑肌受体参与其中。当尼古丁浓度大于3×10⁻⁵M时，去除上皮细胞可强烈抑制收缩，完全消除任何剂量反应效应。ACh诱导的收缩未改变，表明平滑肌完整性良好。我们认为，去除上皮细胞通过去除在上皮内或靠近上皮走行的神经来减弱尼古丁诱导的支气管收缩。组织学研究：在15只雪貂（8只雄性，7只雌性）的气管中，平均体重（±标准差）为1288（±470）克，我们研究了4种去除上皮细胞的技术：（1）用手术刀刀片向后（远离刀刃）轻轻刮擦；（2）将棉签在未打开的气管内移动而不施加侧向压力；（3、4）用棉签轻压（3）或重压（4）打开的气管段黏膜。所有方法在去除上皮细胞方面效率相同（97%-100%），但对基底膜和/或黏膜下组织造成的损伤程度不同。方法（2）对基底膜造成的损伤比其他方法小，但仍去除了近三分之一的基底膜。该研究表明，完全去除上皮细胞是以黏膜下层为代价的，并且给定的“上皮细胞去除”结果也归因于相邻上皮下结构的去除。
