Toniolo Luana, Macchi Veronica, Porzionato Andrea, Paoli Antonio, Marchese-Ragona Rosario, De Caro Raffaele, Reggiani Carlo
Department of Human Anatomy and Physiology, University of Padova, I-35121 Padova, Italy.
Int J Mol Med. 2008 Sep;22(3):375-9.
Laryngeal muscles in mammals are involved in highly specialized functions such as control of air passage, sphincter for airway protection and phonation. In this study, we aimed to assess whether such specialized functions are accompanied by specific distributions of fibre types. To this end, we studied the expression of the isoforms of the heavy subunit of myosin, myosin heavy chain (MyHC), which are considered the molecular markers of fibre types. The pattern of MyHC isoform expression was determined in 5 intrinsic laryngeal muscles: tensors as thyroarytenoid (TA), vocal (Vo), cricothyroid (CT), adductors as transverse arytenoid or interaytenoid (IA), and abductors as posterior cricoarytenoid (PCA), and 2 extrinsic muscles such as thyropharingeal (TPh) and cricopharingeal (CrPh). Muscles were sampled in 14 patients (11 males and 3 females, age 55-75 years) subjected to laryngectomy. MyHC isoforms were separated by SDS-PAGE and quantified by computer assisted densitometry. The comparison between the proportions of MyHC isoforms showed that: i) the three isoforms expressed in trunk and limb muscles (I, IIA and IIX) were present in all muscles examined, ii) the fast or type II MyHC isoforms were predominant in all muscles, representing 60-70% of the total, with no significant differences with respect to muscle types, iii) an additional isoform (indicated as MyHC L) was present in the muscles of the majority of the subjects and was more abundant in Vo and IA. MyHC L was, however, not found in any muscle of the three female patients and was never found in TA and TPh, iv) a great interindividual variability in MyHC distribution was present in all muscles.
哺乳动物的喉肌参与高度专业化的功能，如控制气道、作为气道保护的括约肌以及发声。在本研究中，我们旨在评估这些专业化功能是否伴随着特定的纤维类型分布。为此，我们研究了肌球蛋白重链（MyHC）重亚基同工型的表达，其被认为是纤维类型的分子标志物。在5块喉内肌中确定了MyHC同工型的表达模式：如甲杓肌（TA）、声带肌（Vo）、环甲肌（CT）等张量肌，如杓横肌或杓间肌（IA）等内收肌，以及如环杓后肌（PCA）等外展肌，还有2块喉外肌，如甲咽肌（TPh）和环咽肌（CrPh）。在14例接受喉切除术的患者（11例男性和3例女性，年龄55 - 75岁）中采集肌肉样本。通过SDS - PAGE分离MyHC同工型，并通过计算机辅助密度测定法进行定量。MyHC同工型比例的比较表明：i）在躯干和四肢肌肉中表达的三种同工型（I、IIA和IIX）在所有检测的肌肉中均存在；ii）快速型或II型MyHC同工型在所有肌肉中占主导，占总量的60 - 70%，不同肌肉类型之间无显著差异；iii）大多数受试者的肌肉中存在一种额外的同工型（表示为MyHC L），在Vo和IA中更为丰富。然而，在三名女性患者的任何肌肉中均未发现MyHC L，且在TA和TPh中也从未发现；iv）所有肌肉中MyHC分布均存在很大的个体间差异。
