Nagase T, Matsui H, Sudo E, Matsuse T, Ludwig M S, Fukuchi Y
Department of Geriatrics, Faculty of Medicine, University of Tokyo, Japan.
J Appl Physiol (1985). 1996 Jun;80(6):1872-9. doi: 10.1152/jappl.1996.80.6.1872.
It has been reported that both the elasticity of the cartilage and airway-parenchymal interdependence can modify shortening of the airway smooth muscle and airway narrowing during induced constriction. We hypothesized that induced softening of the cartilage could alter airway compliance and/or the forces of mechanical interdependence, resulting in an increased degree of airway narrowing in response to a contractile stimulus. To test this hypothesis, we compared the effects of changing lung volume on airway resistance (Raw) under baseline conditions and during methacholine (MCh)-induced constriction in papain-treated (n = 6) and control rabbits (n = 6). With use of the alveolar capsule technique, Raw was directly measured under baseline conditions at different levels of end-expiratory transpulmonary pressure (Ptp = 4-12 cmH2O). Then aerosolized MCh was delivered (0.2-25 mg/ml) and measurements were performed at different levels of Ptp (4 and 12 cmH2O). From measured tracheal flow and tracheal and alveolar pressure in open-chest animals during mechanical ventilation (tidal volume = 6 ml/kg, breathing frequency = 1 Hz), we calculated Raw by subtracting tissue resistance from lung resistance. Papain treatment significantly increased Raw both under baseline conditions and after induced constriction. We found that increasing Ptp decreased Raw before and after MCh in both groups; however, the effects of changing Ptp on Raw were less in papain-treated animals. These observations suggest that both cartilage elasticity and mechanical interdependence are important determinants of airway smooth muscle shortening. The observation that volume dependence of Raw was less in papain-treated animals is consistent with the hypothesis that papain effects significant changes in the parenchymal attachments.
据报道，软骨弹性和气道-实质组织相互依存性均可改变诱导性收缩过程中气道平滑肌的缩短及气道狭窄情况。我们推测，诱导软骨软化可能会改变气道顺应性和/或机械相互依存力，从而导致在收缩刺激下气道狭窄程度增加。为验证这一假设，我们比较了木瓜蛋白酶处理组（n = 6）和对照组兔子（n = 6）在基线条件下以及乙酰甲胆碱（MCh）诱导收缩期间，改变肺容积对气道阻力（Raw）的影响。采用肺泡囊技术，在不同的呼气末跨肺压水平（Ptp = 4 - 12 cmH₂O）下直接测量基线条件下的Raw。然后给予雾化的MCh（0.2 - 25 mg/ml），并在不同的Ptp水平（4和12 cmH₂O）下进行测量。通过机械通气（潮气量 = 6 ml/kg，呼吸频率 = 1 Hz）时开胸动物的气管流量、气管及肺泡压力测量值，我们通过从肺阻力中减去组织阻力来计算Raw。木瓜蛋白酶处理在基线条件下和诱导收缩后均显著增加了Raw。我们发现，两组中增加Ptp均会使MCh给药前后的Raw降低；然而，在木瓜蛋白酶处理的动物中，改变Ptp对Raw的影响较小。这些观察结果表明，软骨弹性和机械相互依存性都是气道平滑肌缩短的重要决定因素。木瓜蛋白酶处理的动物中Raw对容积的依赖性较小这一观察结果，与木瓜蛋白酶对实质组织附着产生显著变化的假设一致。
