Ariyasu R G, Deerinck T J, Levinson S R, Ellisman M H
Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla 92093.
J Neurocytol. 1987 Aug;16(4):511-22. doi: 10.1007/BF01668505.
The distributions of (Na+ + K+)ATPase and sodium channels in skeletal muscle fibres and electrocytes were determined by immunofluorescent and immunoelectron microscopic techniques using antibodies against rat and eel (Na+ + K+)ATPase and the eel electric organ sodium channel. The extrajunctional sarcolemma of skeletal muscle was uniformly stained by polyclonal antibodies against (Na+ + K+)ATPase and the sodium channel. The T-tubule system of skeletal muscle was also labelled heavily for both (Na+ + K+)ATPase and the sodium channel. The terminal cisternae of the sarcoplasmic reticulum was stained for (Na+ + K+)ATPase but not sodium channels. At the motor endplate, (Na+ + K+)ATPase-like immunoreactivity was present along the plasmalemma of motor nerve terminals but not along the postsynaptic junctional sarcolemma. Paradoxically, a monoclonal antibody that binds to the alpha form of the catalytic subunit of (Na+ + K+)ATPase from rat hepatocytes and renal tubule cells did not label the enzyme in rat skeletal muscle. In electrocytes, (Na+ + K+)ATPase-like immunoreactivity was concentrated primarily along the plasmalemma and calveolae of the non-innervated face. In contrast, sodium channel-like immunoreactivity was concentrated along the plasmalemma of the innervated face except in the clefts of the postsynaptic membrane. Thus, we conclude that at endplates both the (Na+ + K+)ATPase of rat skeletal muscle and sodium channels of eel electrocytes are not concentrated in the juxtaneuronal postsynaptic membrane. We also interpret the failure of the monoclonal anti-alpha (Na+ + K+)ATPase antibodies to bind to the enzyme in muscle to indicate that the catalytic subunit of skeletal muscle (Na+ + K+)ATPase displays different epitopes than does the alpha subunit of kidney and liver.
利用抗大鼠和鳗鱼（Na⁺ + K⁺）ATP酶以及鳗鱼电器官钠通道的抗体，通过免疫荧光和免疫电子显微镜技术，测定了骨骼肌纤维和电细胞中（Na⁺ + K⁺）ATP酶和钠通道的分布。抗（Na⁺ + K⁺）ATP酶和钠通道的多克隆抗体使骨骼肌的肌膜外区均匀染色。骨骼肌的T小管系统对（Na⁺ + K⁺）ATP酶和钠通道也有强烈标记。肌浆网终池对（Na⁺ + K⁺）ATP酶染色，但对钠通道不染色。在运动终板，运动神经末梢的质膜上有（Na⁺ + K⁺）ATP酶样免疫反应性，但突触后连接肌膜上没有。矛盾的是，一种与大鼠肝细胞和肾小管细胞的（Na⁺ + K⁺）ATP酶催化亚基α形式结合的单克隆抗体，在大鼠骨骼肌中并未标记该酶。在电细胞中，（Na⁺ + K⁺）ATP酶样免疫反应性主要集中在非神经支配面的质膜和小凹处。相比之下，钠通道样免疫反应性集中在神经支配面的质膜上，突触后膜裂隙处除外。因此，我们得出结论，在终板处，大鼠骨骼肌的（Na⁺ + K⁺）ATP酶和鳗鱼电细胞的钠通道都不集中在神经元旁突触后膜。我们还认为，单克隆抗α（Na⁺ + K⁺）ATP酶抗体未能与肌肉中的该酶结合，表明骨骼肌（Na⁺ + K⁺）ATP酶的催化亚基与肾和肝的α亚基显示出不同的表位。
