Tsakiridis T, Wong P P, Liu Z, Rodgers C D, Vranic M, Klip A
Division of Cell Biology, The Hospital for Sick Children, Toronto, Canada.
J Appl Physiol (1985). 1996 Feb;80(2):699-705. doi: 10.1152/jappl.1996.80.2.699.
Muscle fibers adapt to ionic challenges of exercise by increasing the plasma membrane Na+-K+ pump activity. Chronic exercise training has been shown to increase the total amount of Na+-K+ pumps present in skeletal muscle. However, the mechanism of adaptation of the Na+-K+ pump to an acute bout of exercise has not been determined, and it is not known whether it involves alterations in the content of plasma membrane pump subunits. Here we examine the effect of 1 h of treadmill running (20 m/min, 10% grade) on the subcellular distribution and expression of Na+-K+ pump subunits in rat skeletal muscles. Red type I and IIa (red-I/IIa) and white type IIa and IIb (white-IIa/IIb) hindlimb muscles from resting and exercised female Sprague-Dawley rats were removed for subcellular fractionation. By homogenization and gradient centrifugation, crude membranes and purified plasma membranes were isolated and subjected to gel electrophoresis and immunoblotting by using pump subunit-specific antibodies. Furthermore, mRNA was isolated from specific red type I (red-I) and white type IIb (white-IIb) muscles and subjected to Northern blotting by using subunit-specific probes. In both red-I/IIa and white-IIa/IIb muscles, exercise significantly raised the plasma membrane content of the alpha1-subunit of the pump by 64 +/- 24 and 55 +/- 22%, respectively (P < 0.05), and elevated the alpha2-polypeptide by 43 +/- 22 and 94 +/- 39%, respectively (P < 0.05). No significant effect of exercise could be detected on the amount of these subunits in an internal membrane fraction or in total membranes. In addition, exercise significantly increased the alpha1-subunit mRNA in red-I muscle (by 50 +/- 7%; P < 0.05) and the beta2-subunit mRNA in white-IIb muscles (by 64 +/- 19%; P < 0.01), but the alpha2- and beta1-mRNA levels were unaffected in this time period. We conclude that increased presence of alpha1- and alpha2-polypeptides at the plasma membrane and subsequent elevation of the alpha1- and beta2-subunit mRNAs may be mechanisms by which acute exercise regulates the Na+-K+ pump of skeletal muscle.
肌肉纤维通过增加质膜钠钾泵活性来适应运动带来的离子挑战。慢性运动训练已被证明可增加骨骼肌中钠钾泵的总量。然而，钠钾泵对急性运动的适应机制尚未确定，也不清楚这是否涉及质膜泵亚基含量的改变。在此，我们研究了1小时跑步机跑步（20米/分钟，坡度10%）对大鼠骨骼肌中钠钾泵亚基的亚细胞分布和表达的影响。从静息和运动后的雌性斯普拉格-道利大鼠中取出红色I型和IIa型（红-I/IIa）以及白色IIa型和IIb型（白-IIa/IIb）后肢肌肉进行亚细胞分级分离。通过匀浆和梯度离心，分离出粗膜和纯化的质膜，并使用泵亚基特异性抗体进行凝胶电泳和免疫印迹。此外，从特定的红色I型（红-I）和白色IIb型（白-IIb）肌肉中分离出mRNA，并使用亚基特异性探针进行Northern印迹分析。在红-I/IIa和白-IIa/IIb肌肉中，运动分别使泵的α1亚基的质膜含量显著提高了64±24%和55±22%（P<0.05），使α²多肽分别提高了43±22%和94±39%（P<0.05）。运动对内膜部分或总膜中这些亚基的含量未检测到显著影响。此外，运动使红-I肌肉中的α1亚基mRNA显著增加（50±7%；P<0.05），使白-IIb肌肉中的β2亚基mRNA显著增加（64±19%；P<0.01），但在此时间段内α2和β1的mRNA水平未受影响。我们得出结论，质膜上α1和α2多肽的增加以及随后α1和β2亚基mRNA的升高可能是急性运动调节骨骼肌钠钾泵的机制。
