Hämäläinen N, Pette D
Fakultat für Biologie, Universität Konstanz, Germany.
J Muscle Res Cell Motil. 1997 Aug;18(4):401-11. doi: 10.1023/a:1018690629864.
An additional slow fibre type, type I alpha, is detected in diaphragm and appears in fast-twitch hindlimb muscles of rabbit under the influence of altered neuromuscular activity. Type I alpha fibres were delineated from fibres expressing myosin heavy chain I beta (type I beta) by immunohistochemistry with a monoclonal antibody raised against the alpha-cardiac MHCI alpha. When stained for mATPase after acid and alkaline preincubations, some type I alpha fibres resembled type I beta and type IIA fibres, respectively. Some type I alpha fibres displayed dissimilar mATPase staining, indicating heterogeneity of this fibre population. The appearance of numerous type I alpha fibres in stimulated muscles, which in addition contain type IIA and type I beta fibres, suggested that they may be interspaced between types IIA and I beta. Electrophoresis under nondenaturing conditions disclosed an additional isomyosin both in normal diaphragm and stimulated muscles. This band displayed the same mobility as the slowest isomyosin in rabbit masseter muscle. It was recognized by the same monoclonal (anti-alpha-cardiac MHC) antibody used for immunohistochemistry. Therefore, this isomyosin appeared to be very similar, but perhaps not identical to the alpha-cardiac MHC-based isomyosin, probably resulting from discrete differences in the MHC complement. This assumption agrees with additional findings suggesting an even greater heterogeneity of the MHCs than generally assumed. In support of this, we show in atrium and masseter muscles the existence of an additional, electrophoretically distinct MHC isoform which migrates in close vicinity to MHCI alpha.
在膈肌中检测到另一种慢肌纤维类型，即Iα型，并且在神经肌肉活动改变的影响下，它出现在兔的快肌后肢肌肉中。通过使用针对α-心肌肌球蛋白重链Iα（α-MHCIα）产生的单克隆抗体进行免疫组织化学，将Iα型纤维与表达肌球蛋白重链Iβ（Iβ型）的纤维区分开来。在酸和碱预孵育后进行mATPase染色时，一些Iα型纤维分别类似于Iβ型和IIA型纤维。一些Iα型纤维显示出不同的mATPase染色，表明该纤维群体的异质性。在受刺激的肌肉中出现大量Iα型纤维，这些肌肉中还含有IIA型和Iβ型纤维，这表明它们可能间隔在IIA型和Iβ型之间。非变性条件下的电泳显示，在正常膈肌和受刺激的肌肉中都存在另一种异肌球蛋白。该条带显示出与兔咬肌中最慢的异肌球蛋白相同的迁移率。它被用于免疫组织化学的相同单克隆（抗α-心肌MHC）抗体识别。因此，这种异肌球蛋白似乎非常相似，但可能与基于α-心肌MHC的异肌球蛋白不完全相同，这可能是由于MHC组成的离散差异所致。这一假设与其他研究结果一致，这些结果表明MHC的异质性比通常认为的更大。为此，我们在心房和咬肌中显示出存在另一种电泳上不同的MHC同工型，它在靠近MHCIα的位置迁移。
