DelGaudio J M, Sciote J J
Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, USA.
Ann Otol Rhinol Laryngol. 1997 Dec;106(12):1076-81. doi: 10.1177/000348949710601212.
The effects of chronic denervation on the myosin heavy chain (MyHC) content and muscle fiber type composition of rat laryngeal muscles are described. The posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles were removed 3 weeks, 3 months, and 6 months after recurrent laryngeal nerve sectioning. Myofibrillar adenosine triphosphatase staining of cryostat sections was performed, and fiber type percentages were determined. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to separate MyHC isoforms, and densitometry was subsequently used for quantitative analysis. Unoperated animals served as controls. In the PCA muscle, denervation resulted in a progressive reduction in type I MyHC (the slow-contracting isoform) to an almost complete loss at 6 months, with a concomitant increase in type II MyHCs (fast-contracting isoforms, excluding type IIL). Type IIL MyHC (laryngeal-specific isoform) remained relatively constant up to 6 months after denervation. The myosin expression in the TA muscle, which contained only type II MyHCs, remained relatively constant with denervation. Changes in fiber type composition of the muscles described from tissue staining correlated with MyHC content. These findings in laryngeal muscle confirm the dependence of type I MyHC expression upon neural input, as has been found previously in limb skeletal muscles. Since the expression of all MyHCs except the IIL was modified after denervation in the PCA muscle, it is possible that the IIL isoform is maintained by factors that differ from those in the other skeletal myosins.
描述了慢性去神经支配对大鼠喉肌肌球蛋白重链（MyHC）含量和肌纤维类型组成的影响。在喉返神经切断术后3周、3个月和6个月，切除环杓后肌（PCA）和甲杓肌（TA）。对冰冻切片进行肌原纤维腺苷三磷酸酶染色，并测定纤维类型百分比。使用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分离MyHC同工型，随后进行光密度测定以进行定量分析。未手术的动物作为对照。在PCA肌中，去神经支配导致I型MyHC（慢收缩同工型）逐渐减少，在6个月时几乎完全丧失，同时II型MyHCs（快收缩同工型，不包括IIL型）增加。IIL型MyHC（喉特异性同工型）在去神经支配后6个月内保持相对恒定。TA肌中仅含有II型MyHCs，其肌球蛋白表达在去神经支配后保持相对恒定。组织染色所描述的肌肉纤维类型组成的变化与MyHC含量相关。喉肌的这些发现证实了I型MyHC表达对神经输入的依赖性，这与先前在肢体骨骼肌中发现的情况一致。由于PCA肌去神经支配后除IIL型外所有MyHCs的表达均发生改变，因此IIL型同工型可能由与其他骨骼肌肌球蛋白不同的因素维持。
