大鼠胸浅肌肌纤维型组成及其葡萄糖转运蛋白4表达特征

Characteristics of fiber types composition and glucose transporter 4 expression in the rat superficial pectoral muscle

目的:研究大鼠胸浅肌不同肌纤维型的组成分布及其葡萄糖转运蛋白4(GLUT4)表达差异,了解该肌功能。方法:采用Guth-Samaha肌球蛋白ATP酶染色法并稍做改良,对成年SD大鼠胸浅肌冰冻切片进行肌纤维分型研究,并用免疫组织化学法对肌纤维分型后的切片进行GLUT4表达分析。结果:大鼠胸浅肌经肌球蛋白ATP酶染色后可明确分出明亮色白的Ⅰ型纤维和幽暗深褐的Ⅱ型纤维,2种纤维在肌内呈棋盘样均匀分布;Ⅰ型纤维比例为(52·6±6·3)%,Ⅱ纤维为(48·4±5·7)%,两者比例均等。免疫组织化学显色结果显示,GLUT4主要存在于包裹肌束的肌膜和Ⅰ型纤维膜上,而Ⅱ型纤维膜表达不明显。结论:大鼠胸浅肌两型纤维比例均等,属耐力兼速度型肌;Ⅰ型纤维膜的GLUT4表达高于Ⅱ型纤维,表明前者葡萄糖摄取能力高于后者。

Objective： To study the composition and distribution of two muscle fiber types and their different expression of glucose transporter 4 （GLUT4） in rat superficial pectoral muscle and explore its function. Methods： Superficial pectoral muscles of both sides were collected from 10 adult SD rats. 8-μm-thick cryostat sections were transected and then stained with the method of myosin-ATPase following a partially modified method following Guth ＆ Samaha. The GLUT4 expression profiles within different muscle fiber types were determined by immunohistochemistry. Results： The superficial pectoral muscle from SD rats was clearly identified with two different fiber types （Type Ⅰ and Ⅱ ） by the myosin-ATPase staining method. The fibers of Type Ⅰ were stained white, while fibers of Type Ⅱ were stained brown. The distribution pattern of two types of muscle fibers in the superficial pectoral muscle was uniform and chessboard-like. The proportion of Type Ⅰ muscle fibers contained in the muscle was （52.6±6.3）%, which was similar to that of Type Ⅱ fibers [（48. 4±5.7）%] （P〉 0. 05）. Immunohistocbemistry assay showed that the GLUT4 expressed dominantly on the membranes of Type Ⅰ fibers and muscle bundles. Conclusion： The superficial pectoral muscle contains the same proportion of two fiber types, suggesting that it acts as both strength and velocity type of movement. Higher expression of GLUT4 in Type Ⅰ fibers shows that the Type Ⅰ fibers of rat superficial pectoral muscle have a higher ability in glucose uptake than that of Type Ⅱ fibers.