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

本研究的目的是通过生物化学和组织化学澄清1)含有多种肌球蛋白重链（MHC）异构体的杂交纤维在多大程度上存在，2)5和10周龄大鼠正常比目鱼肌近端、中端和远端MHC异构体的表达是否存在区域差异。我们在5周龄动物解剖的单纤维中观察到9种MHC组合，在10周龄动物解剖的单纤维中观察到7种MHC组合。近端地区(5周,26.7 <加减> 7.8%,10周;19.6 <加减> 2.7%)明显(p < 0.05)降低的比例混合纤维比中间(38.5 <加减> 7.9%)和远端(36.2 <加减> 8.1%)地区5岁的周,比远端地区(27.7 <加减> 4.5%)在组织化学地归类为I型纤维的百分比明显高于近端地区(p < 0.05)(5周,64.5 <加减> 1.6%,10周;73.5<正负>3.0%)比远端区（5周；60.6<正负>2.3%，10周；71.3<正负>0.8%）多。此外，IIC型纤维的光密度在从每个切割部分到周围超过2 mm的连续横切面500 μ m间隔内是不均匀的。这些结果表明，在正常大鼠比目鱼肌解剖的单个纤维中，含有多种MHC异构体的杂交纤维大量存在，并且杂交纤维的存在在肌肉区域和/或动物年龄上是不同的。

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.