Immunohistochemical Analysis of Myosin Heavy Chain Expression in Laryngeal Muscles of the Rabbit, Cat, and Baboon

Abstract

S U M M A R Y We studied myosin heavy chain (MyHC) expression and fiber type distribution in laryngeal muscles in the rabbit, cat, and baboon using immunohistochemistry with highly MyHC-specific antibodies. Two types of variation in MyHC expression were found: between muscles of different function within species and within specific muscles between species. Within species, thyroarytenoid (Ta), an adductor, had faster MyHCs and fiber type profiles than the abductor, posterior cricoarytenoid (PCA), which expressed faster MyHCs than the vocal fold tensor, cricothyroid (CT). Between species, laryngeal muscles generally expressed faster MyHCs in small animals than in larger ones: extraocular (EO) MyHC was expressed in the Ta and PCA of the rabbit but not in the cat and baboon, whereas 2B MyHC was expressed in these muscles of the cat but not of the baboon. The CT expressed only MyHC isoforms and fiber types found in the limb muscles of the same species. These results are discussed in light of the hypothesis that the between-species variations in laryngeal muscle fiber types are evolutionary adaptations in response to changes in body mass and respiratory frequency. Within-species variations in fiber types ensure that protective closure of the glottis is always faster than movements regulating airflow during respiration. (J Histochem Cytochem 56:929-950, 2008)

Immunohistochemical Analysis of Laryngeal Muscles in Normal Horses and Horses With Subclinical Recurrent Laryngeal Neuropathy

“…The absence of 2B and EO MyHCs in horse laryngeal muscles is consistent with findings in other large animals-humans (Li et al 2004), baboons (Rhee and Hoh 2008), and cattle (Toniolo et al 2005). These results reflect the notion that variations in fiber types in laryngeal muscles among species represent an adaptation to optimize the control of airway resistance in relation to the respiratory frequency and metabolic rate of the animal (Rhee and Hoh 2008). 2B and EO MyHCs are found only in small mammals such as rats and rabbits, in which respiratory rates are high, and fast abductor and adductors are needed to regulate airflow during inspiration and expiration, respectively.…”

“…The identification of MyHC isoforms in Adreani et al (2006) relied on a comparison of the electrophoretic mobilities of equine and murine MyHCs in SDS-PAGE gels, under the as- sumption that the mobility of each MyHC isoform is independent of species, which clearly cannot be relied upon (Galler et al 1997;Reiser and Kline 1998;Zhong et al 2001). The absence of 2B and EO MyHCs in horse laryngeal muscles is consistent with findings in other large animals-humans (Li et al 2004), baboons (Rhee and Hoh 2008), and cattle (Toniolo et al 2005). These results reflect the notion that variations in fiber types in laryngeal muscles among species represent an adaptation to optimize the control of airway resistance in relation to the respiratory frequency and metabolic rate of the animal (Rhee and Hoh 2008).…”

“…2B and EO MyHCs are found only in small mammals such as rats and rabbits, in which respiratory rates are high, and fast abductor and adductors are needed to regulate airflow during inspiration and expiration, respectively. In animals of intermediate size, such as cats (Rhee and Hoh 2008) and dogs (Wu et al 2000b), 2B but not the faster EO MyHC is expressed. In larger animals, where respiratory rate is low, even 2B MyHC is no longer expressed.…”

Myosin Heavy Chain-2b Transcripts and Isoform Are Expressed in Human Laryngeal Muscles

“…Since some hybrid laryngeal fibres were found to have a substantially higher V o than the fastest type 2x fibres of the limb muscles , the additional MyHC band, migrating between MyHC-1 and 2a, was considered as potentially another fast MyHC isoform. It was assumed to correspond to MyHC-eo, like that found in rat and rabbit laryngeal muscles [Lucas et al, 1995;Merati et al, 1996;Briggs and Schachat, 2000], or even MyHC-2b, like that found in dog and cat laryngeal muscles [Wu et al, 2000b;Rhee and Hoh, 2008]. However, it was recognized neither by the antibody against MyHC-eo nor antibodies against the 2 developmetal isoforms [embryonic MyHC (MyHCemb) and neonatal MyHC (MyHC-neo)] [Shiotani et al, 1999].…”

“…Beside the major MyHC isoforms present in the limb muscles, the presumably very fast MyHC isoform characteristic for extraocular muscles (MyHC-eo) was found to be expressed in rat and rabbit laryngeal muscles [Lucas et al, 1995;Merati et al, 1996;DelGaudio and Sciote, 1997;Shiotani and Flint, 1998;Briggs and Schachat, 2000]. Furthermore, even MyHC-2b, the fastest isoform, which is not expressed in the limb muscles of dog and cat, was demonstrated in the laryngeal muscles of these two species, but not in horse, cattle or baboon [Wu et al, 2000b;Toniolo et al, 2005;Rhee and Hoh, 2008;Rhee et al, 2009].…”