Charlemagne D, Mayoux E, Poyard M, Oliviero P, Geering K
J Biol Chem. 1987 Jul 5;262(19):8941-3.
The present study demonstrates that two forms of the alpha catalytic subunit of the Na,K-ATPase are present in rat heart and originate from cardiomyocytes. They were resolved on sodium dodecyl sulfate-polyacrylamide gel electrophoresis after reduction and alkylation of the sulfhydryl groups. The two forms were identified on immunoblots using two specific antisera against either the alpha subunit from Bufo marinus kidney and the alpha and beta subunits from lamb kidney. Comparison of the two forms to the alkylated Na,K-ATPase from rat kidney (containing one catalytic subunit) and from rat brain (containing alpha and alpha + subunits) suggested that, in rat cardiac myocytes, the form with a fast migration rate (alpha F) corresponds to the alpha subunit of low ouabain affinity and the one with a slow migration rate (alpha S), to a subunit of high ouabain affinity. Thus, the existence of two isoforms of the catalytic subunit in cardiac myocytes accounts well for the biphasic ouabain inhibition of the Na,K-ATPase activity and for the biphasic inotropic responsiveness to cardiac glycosides of the rat heart.
本研究表明，Na，K - ATP酶α催化亚基的两种形式存在于大鼠心脏中，且源自心肌细胞。在对巯基进行还原和烷基化处理后，它们通过十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳得以分离。使用针对海蟾蜍肾脏的α亚基以及羔羊肾脏的α和β亚基的两种特异性抗血清，在免疫印迹上鉴定出了这两种形式。将这两种形式与来自大鼠肾脏（含有一个催化亚基）和大鼠大脑（含有α和α + 亚基）的烷基化Na，K - ATP酶进行比较表明，在大鼠心肌细胞中，迁移速率快的形式（αF）对应于哇巴因亲和力低的α亚基，而迁移速率慢的形式（αS）对应于哇巴因亲和力高的亚基。因此，心肌细胞中催化亚基两种同工型的存在很好地解释了Na，K - ATP酶活性对哇巴因抑制的双相性以及大鼠心脏对强心苷变力反应的双相性。
