Monemi M, Thornell L E, Eriksson P O
Department of Odontology, Umeå University, Sweden.
J Muscle Res Cell Motil. 2000 May;21(4):303-12. doi: 10.1023/a:1005632624826.
The myosin heavy chain (MyHC) content in different parts of, two jaw opening muscle, the human lateral pterygoid and the digastric muscles of five young adult and five elderly subjects (mean age 22 and 73 years, respectively) was determined, using gel electrophoresis and immunohistochemical methods. The lateral pterygoid of both young and elderly contained predominantly slow MyHC, and fast A MyHC was the major fast isoform. In contrast, the digastric was composed of slow, fast A and fast X MyHCs in about equal proportions in both age groups. About half of the lateral pterygoid fibres contained mixtures of slow and fast MyHCs, often together with alpha-cardiac MyHC. In the digastric, co-existence of slow and fast MyHCs was rare, and alpha-cardiac MyHC was lacking. On the other hand, co-expression of fast A and fast X MyHCs was found more often in the digastric than in the lateral pterygoid. In both age groups about half of the digastric IIB fibres contained solely fast X MyHC. In the lateral pterygoid, type IIB fibres with pure fast X MyHC was found in only one subject. The lateral pterygoid in elderly showed a significant amount of fibres with solely fast A MyHC, which were occasionally found in young adults. In the digastric, no significant differences were found between young and elderly, although the muscles of elderly contained lower mean value of slow MyHC, as compared to that of young muscles. It is concluded that the lateral pterygoid and the digastric muscles differ not only in the MyHC composition but also in modifications of the MyHC phenotypes during aging, suggesting that they have separate roles in jaw opening function.
采用凝胶电泳和免疫组织化学方法，测定了5名年轻成年人和5名老年人（平均年龄分别为22岁和73岁）两块开颌肌即人翼外肌和二腹肌不同部位的肌球蛋白重链（MyHC）含量。年轻组和老年组的翼外肌均主要含有慢肌球蛋白重链，快A肌球蛋白重链是主要的快肌亚型。相比之下，两个年龄组的二腹肌均由慢肌球蛋白重链、快A肌球蛋白重链和快X肌球蛋白重链以大致相等的比例组成。约一半的翼外肌纤维含有慢肌球蛋白重链和快肌球蛋白重链的混合物，且常伴有α-心肌肌球蛋白重链。在二腹肌中，慢肌球蛋白重链和快肌球蛋白重链共存的情况很少见，且缺乏α-心肌肌球蛋白重链。另一方面，快A肌球蛋白重链和快X肌球蛋白重链的共表达在二腹肌中比在翼外肌中更常见。在两个年龄组中，约一半的二腹肌IIB型纤维仅含有快X肌球蛋白重链。在翼外肌中，仅在一名受试者中发现了含有纯快X肌球蛋白重链的IIB型纤维。老年组的翼外肌中有大量仅含快A肌球蛋白重链的纤维，在年轻成年人中偶尔也能发现。在二腹肌中，年轻组和老年组之间未发现显著差异，尽管老年组肌肉中慢肌球蛋白重链的平均值低于年轻组肌肉。结论是，翼外肌和二腹肌不仅在肌球蛋白重链组成上不同，而且在衰老过程中肌球蛋白重链表型的变化也不同，这表明它们在开颌功能中具有不同的作用。
