Immunohistochemical Fiber Type Profile in the Human Vocal Muscle

Abstract

SUMMARY: The vocal muscle is a striated muscle with important functions in the emission of laryngeal sound and physiology of the voice. Therefore the knowledge of its constitution is the basis for the prevention and management of voice disorders. We used 10 samples from the middle third of vocal muscles obtained from autopsies of 6 male and 4 female subjects aged between 36 and 71 years. The samples were analyzed with BA-F8 monoclonal antibody to slow type I fibers, and antimyosin HC monoclonal antibody and antimyosin fast clone MY-32 antibody for types IIA, IIB, IIX, and neonatal fibers. We determined the distribution of the muscle fiber types and morphometric characteristics, evaluating the differences by sex and age group. The human vocal muscle presented a het erogeneous formation with a predominance of type II fibers at 51.99%, while type I fibers reached 48.01%; this difference was significant (p 0.05). In conclusion, the human vocal muscle the fibers were predominantly type II fast. The vocal muscle is an intrinsic larynx muscle disposed between the vocal process and the oblong pit of the arytenoid cartilage, and the inner face of the thyroid cartilage near the midline. This muscle is the most important element of the vocal folds due to its role in the shortening and relaxation of these folds. Histologically it is composed of striated skeletal muscle tissue, grouped in bundles that are arranged to determine the upper portions, and lower ave- rage muscle (Di Fiore, 2001; Latarjet & Ruiz Liard, 1997). The altered function of the muscles of the larynx is presented in various diseases of the voice, these changes have expression in the metabolism of muscle fibers in its organization and morphological appearance, as histochemical and immunohistochemical study of muscle fibers is a valuable tool for evaluation. The histochemical differentiation of muscle fibers supports the diagnosis of many myopathies (Hebling & Esquisatto, 2005). The preferred method for the differentiation of muscle fibers is based on the histochemical reaction for the identification of the enzyme nicotinamide dinucleotides tetrazolium reductase (NADH-