title: Age-related alterations in myosin heavy chain isoforms in rat intrinsic laryngeal muscles.
abstract: Deficits in voice and swallowing are found in the elderly, but the underlying neuromuscular mechanisms are unclear. A potential mechanism may be denervation-induced muscle fiber transformation to a slower-contracting type of muscle fiber. This study examined young, old, and denervated rat laryngeal muscles (lateral thyroarytenoid, lateral cricoarytenoid, and posterior cricoarytenoid) to examine differences in myosin heavy chain (MHC) composition. Results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses indicated that all muscles were composed predominately of type IIB MHC. With aging and denervation, type IIB was reduced and type IIX, a slower-contracting isoform, was increased in the lateral thyroarytenoid and lateral cricoarytenoid muscles. In the posterior cricoarytenoid muscle, the MHC composition was relatively unchanged. These findings suggest that aging may affect laryngeal adductory function by altering muscle fiber type composition to a slower-contracting isoform, in a manner similar to that observed with denervation.
authors.affiliation: Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin, Madison, USA.
authors.forename: Tatsutoshi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Nadine P
authors.initials: NP
authors.lastname: Connor
authors.forename: Kyungah
authors.initials: K
authors.lastname: Lee
authors.forename: Diane M
authors.initials: DM
authors.lastname: Bless
authors.forename: Charles N
authors.initials: CN
authors.lastname: Ford
authors.forename: Katsuhide
authors.initials: K
authors.lastname: Inagi
mesh_terms: D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000818:Animals; D003720:Densitometry; D004591:Electrophoresis, Polyacrylamide Gel; D007821:Laryngeal Muscles / Q000737:chemistry* / Q000294:innervation / Q000502:physiology*; D009119:Muscle Contraction; D009121:Muscle Denervation; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018995:Myosin Heavy Chains / Q000032:analysis*; D020033:Protein Isoforms / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D020033:Protein Isoforms; D018995:Myosin Heavy Chains