家兔半膜肌各亚部肌球蛋白重链表达差异的实验研究

Experimental studies on the differential expression of myosin heavy chain mRNA of various compartments of semimembranosus in rabbit

目的利用家兔半膜肌各亚部肌纤维类型的分布特征,观察骨骼肌两型肌纤维肌球蛋白重链(MHC)的构成特点,为进一步探讨两型肌纤维的区别以及两型肌纤维转化机制奠定基础。方法取成年家兔半膜肌,通过改良肌球蛋白ATP酶染色法观察半膜肌四个亚部肌纤维类型的构成,应用RT-PCR方法检测各亚部4种MHC亚型mRNA的表达情况。结果固有半膜肌只含有慢肌(Ⅰ型)肌纤维,表达MHCⅠ型和少量MHCⅡa型基因。副半膜肌腹侧亚部除含有少量Ⅰ型肌纤维外,主要含有快肌(Ⅱ型)肌纤维,表达少量MHCⅠ型基因以及MHCⅡa、MHCⅡb和MHCⅡx型基因等四种类型;而副半膜肌背侧和外侧亚部只含有Ⅱ型肌纤维,仅表达MHCⅡa、MHCⅡb和MHCⅡx型基因。结论家兔半膜肌各亚部肌纤维类型几乎均呈单一类型分布。固有半膜肌亚部主要表达MHCⅠ型基因;副半膜肌各亚部主要表达MHCⅡa、MHCⅡb和MHCⅡx型基因,以MHCⅡx型基因为主,各亚部之间存在细微差别。

Objective The feature of the rabbit semimembranosus is that its various compartments only possess one muscle fiber type： slow muscle fiber（typeⅠ） or fast muscle fibers（typeⅡ）.To explore differences of the two types of skeletal muscle fiber,the expression of various myosin heavy chains（MHC） isoforms was observe in four compartments of the rabbit semimembranosus.Methods The rabbit semimembranosus was obtained from 10 adult rabbits.The composition of skeletal muscle fiber type was observed in four compartments of the rabbit semimembranosus by myosin ATPase staining method and the expression of various myosin heavy chain（MHC） isoforms was observe by RT-PCR.Results The inherent semimembranosus only contained slow muscle fiber（typeⅠ） and expressed MHCⅠand MHCⅡ a.The ventral compartment of semimembranosus mainly contained fast muscle fibers（typeⅡ）and a little slow muscle fiber（typeⅠ） and expressed MHCⅡa.MHCⅡb and Ⅱx and a few MHCⅠ.while its dorsal and lateral compartment only contained fast muscle and only expressed MHCⅡ a,MHCⅡ b and MHCⅡ x.Conclusion Various compartments of the rabbit semimembranosus almost possessed one muscle fiber type and accordingly expressed various myosin heavy chain（MHC） isoforms.