Myosin heavy chain composition of rat middle ear muscles

Hak Hyun Jung, Seung Hoon Han, Soon Yuhl Nam, Young Ho Kim, Jeung Lim Kim

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Objective - To quantitatively analyze myosin heavy chain (MHC) mRNA composition in two rat middle ear muscles (the tensor tympani and stapedius) using competitive polymerase chain reaction (PCR). Material and Methods - An exogenous template, including oligonucleotide sequences specific for the seven rat MHCs (2A, 2B, 2X, 2L/EOM, embryonic, neonatal and β-cardiac) as well as β-actin, was constructed and used as the competitor. Results - The tensor tympani and stapedius contained all MHC isoforms except 2L. The tensor tympani contained approximately equal proportions of 2X (40.4%±6.5%) and 2A (34.0%±1.3%) MHCs, with a smaller percentage of 2B (16.6%±1.5%) and neonatal (7.5%±0.6%) MHCs, while β-cardiac and embryonic MHCs were minimally expressed. The stapedius contained predominantly 2X (58.0%±4.2%) and 2A (32.3%±6.7%) MHCs, with a smaller percentage of 2B (7.4%±0.2%) and β-cardiac (1.9%±0.1%) MHCs. Neonatal and embryonic MHCs were detected at very low levels. Conclusion - These results suggest that two middle ear muscles, which are mainly composed of two fast-twitching myosins (2X and 2A MHCs), contract fast and are fatigue-resistant.

Original languageEnglish
Pages (from-to)569-573
Number of pages5
JournalActa Oto-Laryngologica
Issue number5
Publication statusPublished - 2004
Externally publishedYes

Bibliographical note

Funding Information:
This study was supported by the Brain Korea 21 Project of Korea University, and by a grant (00-178) from the Asan Institute for Life Sciences, Seoul, South Korea.


  • Branchial muscle
  • Muscle contraction
  • Rat

ASJC Scopus subject areas

  • Otorhinolaryngology


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