大鼠胸深肌GLUT4表达的肌纤维型特异性

Fiber type specificity of GLUT4 expression in the rat deep pectoral muscle

目的:研究大鼠胸深肌不同肌纤维型的组成分布及其葡糖转运蛋白4(GLUT4)表达差异,借以了解胸深肌功能。方法:采用GUTH-SAMAHA肌球蛋白ATP酶染色法并稍做改良,对成年SD大鼠胸深肌冰冻切片进行肌纤维分型研究,并用免疫组织化学方法对肌纤维分型后的切片进行GLUT4表达分析。结果:2种骨骼肌纤维在大鼠胸深肌内呈棋盘样均匀分布;Ⅱ型肌纤维比例为(64.8±6.3)%,而Ⅰ型肌纤维仅占(35.2±4.6)%,前者明显高于后者(P<0.01)。GLUT4主要存在于Ⅰ型肌纤维膜及包裹肌束的肌膜上,而Ⅱ型肌纤维膜表达不明显。结论:大鼠胸深肌以Ⅱ型肌纤维为主,偏重于力量和速度型肌;Ⅰ型肌纤维膜的GLUT4表达高于Ⅱ型肌纤维,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 differences in glucose trasporter 4（GLUT4） expression of SD rat deep pectoral muscle in order to learn its functions.Methods：Deep 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 Guth-Samaha myosin-ATPase followed by a partially modified procedure to determine the muscle fiber types.Then,the GLUT4 expression profiles within different muscle fiber types were analyzed by immunohistochemistry.Results：Deep pectoral muscle from SD rats can be clearly identified as two different fiber types which are type I and typeⅡ,the distribution pattern of which in deep pectoral muscle is uniform and chessboard-like.The proportion of typeⅡ muscle fibers in Deep pectoral muscle was（64.8±6.3）%,much higher than that of type I fibers which was（35.2±4.6）%（P 〈 0.01）.Immunohistochemistry assay showed that GLUT4 expressed mainly on the membranes of type I fibers and muscle bundles,and little on those of type II fibers.Conclusion：Type II fibers are dominant in rat deep pectoral muscle,implying that the muscle participates more in the movement of strength and speed.Higher expression of GLUT4 in typeⅠfibers suggests that the typeⅠfibers have a higher ability in glucose uptake than typeⅡfibers.