Pedrosa F, Butler-Browne G S, Dhoot G K, Fischman D A, Thornell L E
Department of Anatomy, University of Umeå, Sweden.
Histochemistry. 1989;92(3):185-94. doi: 10.1007/BF00500917.
The composition of adult rat soleus muscle spindles, with respect to myosin heavy chain isoforms and M-band proteins, was studied by light-microscope immunohistochemistry. Serial sections were labelled with antibodies against slow tonic, slow twitch, fast twitch and neonatal myosin isoforms as well as against myomesin, M-protein and the MM form of creatine kinase. Intrafusal fiber types were distinguished according to the pattern of ATPase activity following acid and alkaline preincubations. Nuclear bag1 fibers were always strongly stained throughout with anti-slow tonic myosin, were positive for anti-slow twitch myosin towards and in the C-region but were unstained with anti-fast twitch and anti-neonatal myosins. The staining of nuclear bag2 fibers was in general highly variable. However, they were most often strongly stained by anti-slow tonic myosin in the A-region and gradually lost this reactivity towards the poles, whereas a positive reaction with anti-slow twitch myosins was found along the whole fiber. Regional staining variability with anti-neonatal and anti-fast myosins was apparent, often with decreasing intensity towards the polar regions. Nuclear chain fibers showed strong transient reactivity with anti-slow tonic myosin in the equatorial region, did not react with anti-slow twitch and were always evenly stained by anti-fast twitch and anti-neonatal myosins. All three intrafusal fiber types were stained with anti-myomesin. Nuclear bag1 fibers lacked staining for M-protein, whereas bag2 fibers displayed intermediate staining, with regional variability, often increasing in reactivity towards the polar regions. Chain fibers were always strongly stained by anti-M-protein. The MM form of creatine kinase was present in all three fiber types, but bag1 fibers were less reactive and clear striations were not observed, in contrast to bag2 and chain fibers. Out of 38 cross sectioned spindles two were found to have an atypical fiber composition (lack of chain fibers) and a rather diverse staining pattern for the different antibodies tested. Taken together, the data show that in adult rat soleus, slow tonic and neonatal myosin heavy chain isoforms are only expressed in the muscle spindle fibers and that each intrafusal fiber type has a unique, although variable, composition of myosin heavy chain isoforms and M-band proteins. We propose that both motor and sensory innervation might be the determining factors regulating the variable expression of myosin heavy chain isoforms and M-band proteins in intrafusal fibers of rat muscle spindles.
通过光学显微镜免疫组织化学方法，研究了成年大鼠比目鱼肌肌梭在肌球蛋白重链亚型和M带蛋白方面的组成。连续切片用抗慢强直性、慢收缩、快收缩和新生肌球蛋白亚型的抗体以及抗肌间线蛋白、M蛋白和肌酸激酶MM型的抗体进行标记。根据酸和碱预孵育后ATP酶活性的模式区分梭内纤维类型。核袋1纤维始终被抗慢强直性肌球蛋白强烈染色，在朝向C区及C区内对抗慢收缩肌球蛋白呈阳性反应，但用抗快收缩和抗新生肌球蛋白染色不着色。核袋2纤维的染色总体上变化很大。然而，它们最常被A区的抗慢强直性肌球蛋白强烈染色，并逐渐向两极失去这种反应性，而沿整个纤维发现与抗慢收缩肌球蛋白呈阳性反应。抗新生和抗快肌球蛋白的区域染色变异性明显，通常向极区强度降低。核链纤维在赤道区与抗慢强直性肌球蛋白有强烈的瞬时反应，与抗慢收缩肌球蛋白无反应，并且始终被抗快收缩和抗新生肌球蛋白均匀染色。所有三种梭内纤维类型都用抗肌间线蛋白染色。核袋1纤维缺乏M蛋白染色，而袋2纤维显示中等染色，具有区域变异性，通常向极区反应性增加。链纤维始终被抗M蛋白强烈染色。肌酸激酶MM型存在于所有三种纤维类型中，但与袋2纤维和链纤维相比，袋1纤维反应性较低，未观察到明显条纹。在38个横切的肌梭中，发现两个具有非典型纤维组成（缺乏链纤维），并且对所测试的不同抗体有相当多样的染色模式。综上所述，数据表明在成年大鼠比目鱼肌中，慢强直性和新生肌球蛋白重链亚型仅在肌梭纤维中表达，并且每种梭内纤维类型都有独特的、尽管可变的肌球蛋白重链亚型和M带蛋白组成。我们提出运动和感觉神经支配可能是调节大鼠肌梭梭内纤维中肌球蛋白重链亚型和M带蛋白可变表达的决定因素。
