慢性心肌缺血大鼠膈肌舒缩功能和结构的变化

Functional and structural changes of diaphragm in rats with chronic myocardiac ischemia

目的 探讨慢性心肌缺血大鼠膈肌结构和功能的变化及其机制。方法 2 4只大鼠随机分为 2组 ,实验组结扎冠状动脉分支 ,复制慢性心肌缺血模型 ;对照组仅做开胸手术。用组化染色法对膈肌纤维进行分类分析 ,做膈肌条等张收缩实验分析膈肌舒缩功能。结果 慢性心肌缺血大鼠膈肌Ⅰ类纤维比例增加 (4 0 %± 1%→ 48%± 1% ) ,Ⅱa类纤维比例明显下降 (4 3%± 2 % 36 %± 2 % ) ,两类纤维横截面积均下降 ,同时膈肌舒缩功能也明显减退。

Objective To study the structural and functional changes of diaphragm in rats with chronic myocardiac ischemia.Methods Twenty-four rats were equally divided into two groups:experimental group,whose left coronary arterial branches were ligated to induce myocardiac ischemia (MI);control group,shame-operated.Three months after the operation,contractile functions of diaphragm were measured by isometric test,and the fiber proportions and cross-sectional areas(CSA) of diaphragm were determined by histochemical methods.Results Compared with control group,diaphragm contractility decreased significantly and the CSA of type Ⅰ and type Ⅱa fibers reduced by 7.6% and 15.6%,respectively,in rats with MI,while the proportion of type Ⅰ fibers increased significantly (40±1% to 48±1%) and that of type Ⅱa fibers decreased (43±2% to 36±2%) in the experimental group.Conclusions Chronic myocardiac ischemia may cause selected atrophy of diaphragm which results in decrease of diaphragm contractility.