Diversity of myosin heavy chain isoform expression in rat single muscle fibers

本研究的目的是生物化学和组织化学澄清1）在何种程度上存在的杂交纤维含有多种肌球蛋白重链（MHC）异构体和2）是否存在区域差异，在近端，在5周龄和10周龄大鼠比目鱼肌中、远段肌纤维中观察到9种MHC的组合，5周龄动物和来自10周龄动物的7种类型组合。在5周龄时，近端区域（5周; 26.7 ± <plus-minus>7.8%，10周; 19.6 <plus-minus>± 2.7%）的混合纤维百分比显著（p&lt;0.05）低于中间区域（38.5 ± <plus-minus>7.9%）和远端区域（36.2 <plus-minus>± 8.1%），在两个年龄组中<plus-minus>，近端区域（5周; 64.5 <plus-minus>± 1.6%，10周; 73.5 ± <plus-minus>3.0%）的I型纤维百分比显著高于远端区域（5周; 60.6 ± <plus-minus>2.3%，10周; 71.3 ± <plus-minus>0.8%）（p&lt;0.05）。此外，IIC型纤维的光密度是不均匀的，在连续的横截面在500 μ m的间隔，从每个切割部分的周边超过2毫米d这些结果表明，混合纤维含有多种MHC亚型存在相当大的单纤维解剖正常大鼠比目鱼肌，和混合纤维的存在不同的肌肉区域和/或动物的年龄。

The objectives of the present study were biochemically and histochemically clarified 1) to what extent the hybrid fiber containing multiple myosin heavy chain (MHC) isoforms exist and 2) to whether the regional differences exist in MHC isoforms expression among the proximal, middle and distal regions in the normal soleus muscles at 5 and 10 week old rats.We observed 9 types combination of MHC in the single fiber dissected from 5-week age animals and 7 types combination from 10-week age animals. The proximal region (5 weeks ; 26.7<plus-minus>7.8%, 10 weeks ; 19.6<plus-minus>2.7%) had a significantly (p<0.05) lower percentage of hybrid fibers than those of the middle (38.5<plus-minus>7.9%) and distal (36.2<plus-minus>8.1%) regions at age 5 weeks, than that of the distal region (27.7<plus-minus>4.5%) atThe percentage of histochemically classified as type I fiber was significantly higher (p<0.05) in the proximal region (5 weeks ; 64.5<plus-minus>1.6%, 10 weeks ; 73.5<plus-minus>3.0%) than that in the distal region (5 weeks ; 60.6<plus-minus>2.3%, 10 weeks ; 71.3<plus-minus>0.8%) in both age groups. Furthermore, the optical densities of type IIC fibers were nonuniform in successive transverse sections at 500 mum intervals from each cut portion to the periphery over 2 mm dThese results show that the hybrid fiber containing multiple MHC isoforms exist considerably in the single fiber dissected from normal rat soleus muscles, and the existence of hybrid fiber differs in the muscle region and/or the age of animals.