Jiang T X, Cairns A, Road J D, Wilcox P G
Department of Medicine, University of British Columbia, Vancouver, Canada.
Am J Respir Crit Care Med. 1996 Dec;154(6 Pt 1):1778-83. doi: 10.1164/ajrccm.154.6.8970370.
The present study was designed to examine whether clenbuterol (CLEN) could reduce dexamethasone (DEX)-induced diaphragm dysfunction. We studied four groups of New Zealand white (NZW) rabbits, each receiving one of the following daily injections subcutaneously for 2 wk: saline (control), DEX 3 mg/kg, DEX 3 mg/kg + CLEN 2 mg/kg, and CLEN 2 mg/kg. Diaphragm fiber cross-sectional areas (CSA) were measured. Twitch transdiaphragmatic pressure (Pdi) and tetanic Pdi were measured during bilateral phrenic stimulation both before and after 60 min of inspiratory resistive loading (IRL). DEX produced a marked atrophy of type IIa and type IIb diaphragm fibers. This diaphragm atrophy was prevented by CLEN in the DEX plus CLEN group. CLEN alone increased CSAs of all three types of diaphragm fibers. Significant reductions in twitch Pdi and tetanic Pdi at all stimulation frequencies both before and after IRL were observed similarly in the DEX group as well as in the DEX plus CLEN group compared with the control animals. We conclude that DEX produces significant diaphragm atrophy and decreases diaphragmatic contractility. CLEN produces hypertrophy of the diaphragm and minimizes diaphragm atrophy induced by DEX, but it has no demonstrable protective effect on DEX-induced diaphragm dysfunction.
本研究旨在探讨克伦特罗（CLEN）是否能减轻地塞米松（DEX）诱导的膈肌功能障碍。我们研究了四组新西兰白兔，每组每天皮下注射以下药物之一，持续2周：生理盐水（对照组）、3 mg/kg DEX、3 mg/kg DEX + 2 mg/kg CLEN、2 mg/kg CLEN。测量膈肌纤维横截面积（CSA）。在吸气阻力负荷（IRL）60分钟前后双侧膈神经刺激期间，测量单次膈肌跨膈压（Pdi）和强直Pdi。DEX导致IIa型和IIb型膈肌纤维明显萎缩。在DEX加CLEN组中，CLEN可防止这种膈肌萎缩。单独使用CLEN可增加所有三种类型膈肌纤维的CSA。与对照动物相比，DEX组以及DEX加CLEN组在IRL前后所有刺激频率下的单次Pdi和强直Pdi均显著降低。我们得出结论，DEX可导致明显的膈肌萎缩并降低膈肌收缩力。CLEN可使膈肌肥大，并使DEX诱导的膈肌萎缩最小化，但对DEX诱导的膈肌功能障碍没有明显的保护作用。
