Huey K A, Bodine S C
Biomedical Sciences Program, University of California, San Diego, School of Medicine, USA.
Am J Physiol. 1996 Dec;271(6 Pt 1):C2016-26. doi: 10.1152/ajpcell.1996.271.6.C2016.
Myosin heavy chain (MHC) expression was studied in rat soleus and tibialis anterior (TA) at the mRNA and protein levels following reinnervation 8 and 32 wk after sciatic nerve injury. A sciatic nerve crush or transection injury was produced in the midthigh region of adult female Sprague-Dawley rats. A ribonuclease protection assay was developed to measure four of the adult MHCs (I, IIa, IIx, IIb) in a single sample. MHC mRNA and protein were measured and compared in the same muscles. Eight and thirty-two weeks after a crush injury, the MHC mRNA profiles were similar to control with the exception of soleus MHC IIa and TA MHC IIb, which were significantly less than control at both time points. In contrast, reinnervation of the soleus following a sciatic nerve transection injury resulted in an MHC isoform shift characterized by increases in the relative amounts of fast myosin (IIa and IIx) and a decrease in slow myosin. As expected, significant changes first occurred at the mRNA level followed by changes in protein expression. Thirty-two weeks after transection injury and repair, the primary MHC mRNA isoform in the soleus was MHC IIx. Moreover, at 32 wk, MHC IIb mRNA was detected in 50% of the reinnervated soleus following a transection injury. Reinnervation of the TA following sciatic nerve transection led to replacement of the MHC IIb isoform with MHC IIx.
在坐骨神经损伤后8周和32周重新神经支配后，在mRNA和蛋白质水平上研究了大鼠比目鱼肌和胫前肌（TA）中的肌球蛋白重链（MHC）表达。在成年雌性Sprague-Dawley大鼠的大腿中部区域造成坐骨神经挤压或横断损伤。开发了一种核糖核酸酶保护试验来在单个样本中测量四种成年MHC（I、IIa、IIx、IIb）。在相同的肌肉中测量并比较了MHC mRNA和蛋白质。挤压损伤后8周和32周，除比目鱼肌MHC IIa和TA肌MHC IIb外（这两种在两个时间点均显著低于对照），MHC mRNA谱与对照相似。相反，坐骨神经横断损伤后比目鱼肌的重新神经支配导致MHC同工型转变，其特征是快肌球蛋白（IIa和IIx）的相对量增加，慢肌球蛋白减少。正如预期的那样，显著变化首先发生在mRNA水平，随后是蛋白质表达的变化。横断损伤和修复后32周，比目鱼肌中的主要MHC mRNA同工型是MHC IIx。此外，在横断损伤后32周，50%重新神经支配的比目鱼肌中检测到MHC IIb mRNA。坐骨神经横断后TA的重新神经支配导致MHC IIb同工型被MHC IIx取代。
