Maccatrozzo L, Patruno M, Toniolo L, Reggiani C, Mascarello F
Department of Experimental Veterinary Sciences, University of Padua, Italy.
Eur J Histochem. 2004 Oct-Dec;48(4):357-66.
Myosin heavy chain isoforms (MHC) of adult skeletal muscles are codified by four genes named: slow, or type 1, and fast types 2A, 2X and 2B. The slow, 2A and 2X isoforms have been found expressed in all mammalian species studied so far whereas there is a large inter-species variability in the expression of MHC-2B. In this study histochemistry (m-ATPase), immunohistochemistry with the use of specific monoclonal antibodies and RT-PCR were combined together to assess whether the MHC-2B gene is expressed in bovine muscles. ATPase staining and RT-PCR experiments showed that three MHC isoforms (1, 2A, 2X) were expressed in trunk and limb muscles. Slow or type 1 expression was confirmed using a specific antibody (BA-F8) whereas the detection of fast MHC isoforms were validate by means of BF-35 antibody although not by the SC-71 antibody. MHC-2B was absent in limb and trunk muscles, but was present in specialized eye muscles (rectus lateralis and retractor bulbi) as consistently showed by RT-PCR and reactivity with a specific antibody (BF-F3). Interestingly, a cardiac isoform, MHC-a-cardiac was found to be expressed not only in extraocular muscles but also in masticatory muscles as masseter.
成年骨骼肌的肌球蛋白重链亚型（MHC）由四个基因编码，分别命名为：慢肌型或1型，以及快肌型2A、2X和2B。到目前为止，在所有研究过的哺乳动物物种中都发现了慢肌型、2A型和2X型亚型的表达，而MHC-2B的表达在不同物种间存在很大差异。在本研究中，将组织化学（m-ATP酶）、使用特异性单克隆抗体的免疫组织化学和逆转录聚合酶链反应（RT-PCR）结合起来，以评估MHC-2B基因是否在牛肌肉中表达。ATP酶染色和RT-PCR实验表明，三种MHC亚型（1型、2A型、2X型）在躯干和四肢肌肉中表达。使用特异性抗体（BA-F8）证实了慢肌型或1型的表达，而通过BF-35抗体验证了快肌型MHC亚型的检测，尽管SC-71抗体未能验证。RT-PCR和与特异性抗体（BF-F3）的反应性一致显示，四肢和躯干肌肉中不存在MHC-2B，但在特殊的眼肌（外直肌和眼球退缩肌）中存在。有趣的是，发现一种心脏亚型MHC-α-心脏不仅在眼外肌中表达，而且在咀嚼肌如咬肌中也有表达。
