Myosin heavy chain composition in human laryngeal muscles

Objectives: Myosin heavy chain (MHC) composition of human thyroarytenoid (T A), lateral cricoarytenoid (LCA), interarytenoid (IA), vocalis, posterior c ricoarytenoid (PCA), and cricothyroid muscles were examined using sodium do decyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western bol t techniques. The presence of superfast MHC was also assessed using antibod ies directed against the extraocular MHC, Study Design: MHC protein was ana lyzed using fresh human laryngeal muscles. Methods: Laryngeal muscles excis ed from cadavers were processed for SDS-PAGE, The composition of MHC isofor ms was determined by densitometry, Western blot was carried out to identify specific bands. Results: MHC types IIA and IIB are the predominant MHC com ponents in human laryngeal muscles. The adductor muscles-TA, LCA, and IA-ha ve a higher percentage of type IIB MHC and a lower percentage of type I whe n compared with the abductor-PCA The rank file order for type IIB MHC compo sition (TA>LCA greater than or equal to IA>PCA) is the same in all specimen s, A band migrating between type IIA and type I was observed in several spe cimens, Although similar to type IIL in rats, this atypical band did not re act with antiextraocular MHC antibody on Western blot. Conclusion: Characte rization of laryngeal muscles determined by the composition of MHC is corre lated with function and neural input. Human laryngeal muscle is characteriz ed by a predominance of fast-type MHCs in laryngeal closing muscle and mixe d fast-slow type MHCs in respiratory and phonatory muscle groups. Although an atypical myosin band similar to type IIL (superfast) MHC in rat was iden tified, it did not react with anti-extraocular MHC antibody.