Lucas C A, Rughani A, Hoh J F
Department of Physiology, University of Sydney, NSW, Australia.
J Muscle Res Cell Motil. 1995 Aug;16(4):368-78. doi: 10.1007/BF00114502.
The intrinsic laryngeal muscles of mammals are functionally heterogeneous, some of these muscles (e.g. the thyroarytenoid) contract extremely rapidly, like extraocular muscle, whilst others (e.g. the cricothyroid) contract as fast as limb fast muscle. The extraordinarily rapid contraction speed of extraocular muscles is associated with a fast myosin not found in limb muscles. In this work we explored the possibility that the thyroarytenoid muscle may also express this extraocular-specific fast myosin by raising a monoclonal antibody (mab 4A6) against its heavy chain. Electrophoretic separation of native isomyosins revealed that both the extraocular and the thyroarytenoid have two similar bands migrating ahead of bands found in limb fast or cricothyroid myosins. These two bands bound mab 4A6. The thyroarytenoid muscle can be divided into two divisions, a vocalis division which is important in phonation and an external division which functions in closing the glottis. Fibres in the vocalis are heterogeneous, some stain with mab 4A6, whilst others stain with mabs against limb myosin heavy chains. Fibres in the external division stain almost homogeneous with mab 4A6. The immunohistochemical staining pattern in the cricothyroid muscle resembled that of fast limb muscle: no fibres stained with mab 4A6. Thus, the high speed of contraction of the thyroarytenoid is associated with the same myosin heavy chain found in extraocular muscles, this characteristic is presumably an evolutionary adaptation for rapid closure of the glottis to enhance airway defense mechanisms.
哺乳动物的喉内肌在功能上具有异质性，其中一些肌肉（如甲杓肌）收缩极快，类似于眼外肌，而另一些肌肉（如环甲肌）收缩速度与肢体快肌一样快。眼外肌异常快速的收缩速度与肢体肌肉中未发现的一种快速肌球蛋白有关。在这项研究中，我们通过制备针对其重链的单克隆抗体（单克隆抗体4A6），探讨了甲杓肌是否也可能表达这种眼外肌特异性快速肌球蛋白的可能性。天然同工型肌球蛋白的电泳分离显示，眼外肌和甲杓肌都有两条类似的条带，其迁移速度快于肢体快肌或环甲肌肌球蛋白中的条带。这两条带与单克隆抗体4A6结合。甲杓肌可分为两个部分，一个是在发声中起重要作用的声带部分，另一个是在关闭声门中起作用的外部部分。声带中的纤维是异质的，一些用单克隆抗体4A6染色，而另一些用针对肢体肌球蛋白重链的单克隆抗体染色。外部部分的纤维用单克隆抗体4A6染色几乎均匀。环甲肌中的免疫组织化学染色模式类似于肢体快肌：没有纤维用单克隆抗体4A6染色。因此，甲杓肌的高速收缩与眼外肌中发现的相同肌球蛋白重链有关，这一特征可能是一种进化适应，用于快速关闭声门以增强气道防御机制。
