Van Der Heijden H F, Dekhuijzen P N, Folgering H, Ginsel L A, Van Herwaarden C L
Department of Pulmonary Diseases, University Hospital Nijmegen, 6500 HB Nijmegen, The Netherlands.
J Appl Physiol (1985). 1998 Jul;85(1):215-22. doi: 10.1152/jappl.1998.85.1.215.
The aim of the present study was to investigate the effect of chronic long-term clenbuterol treatment (1 mg/kg subcutaneously twice a day for 12 wk) on diaphragm morphology and function in emphysematous (EH) and normal hamsters (NH). Clenbuterol increased body weight, diaphragm weight, and skeletal muscle weight in both EH and NH to a similar extent. In the diaphragm, clenbuterol significantly increased myosin heavy chain type I, IIa, and IIx muscle fiber cross-sectional areas by approximately 35-55% in both EH and NH. This response to clenbuterol treatment was not significantly different between EH and NH diaphragm. In EH, twitch force (Pt), maximal tetanic force, and force-frequency curve were significantly reduced compared with NH. In EH, clenbuterol increased Pt by approximately 10%, restoring Pt to NH level. A similar improvement was observed in the force-frequency characteristics. Clenbuterol did not alter contractile properties in NH. In conclusion, long-term clenbuterol treatment resulted in an increased size of all diaphragm muscle fiber types in both NH and EH. Clenbuterol completely abolished the reduced force generation induced by emphysema.
本研究的目的是调查长期慢性使用克伦特罗治疗（皮下注射1毫克/千克，每天两次，持续12周）对肺气肿仓鼠（EH）和正常仓鼠（NH）膈肌形态和功能的影响。克伦特罗使EH和NH的体重、膈肌重量和骨骼肌重量增加的程度相似。在膈肌中，克伦特罗使EH和NH的I型、IIa型和IIx型肌球蛋白重链肌纤维横截面积显著增加约35%-55%。EH和NH膈肌对克伦特罗治疗的这种反应没有显著差异。与NH相比，EH的单收缩力（Pt）、最大强直收缩力和力-频率曲线显著降低。在EH中，克伦特罗使Pt增加约10%，将Pt恢复到NH的水平。在力-频率特性方面也观察到类似的改善。克伦特罗没有改变NH的收缩特性。总之，长期使用克伦特罗治疗导致NH和EH中所有膈肌肌纤维类型的大小增加。克伦特罗完全消除了肺气肿引起的力量产生减少。
