Brodsky J L
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
Am J Physiol. 1990 May;258(5 Pt 1):C812-7. doi: 10.1152/ajpcell.1990.258.5.C812.
The sensitivity of the synaptosomal Na(+)-K(+)-ATPase to insulin was examined and found to be stimulated by the hormone when physiological intracellular sodium concentrations were present. Activation was not mediated by a sodium influx into the vesicles, as shown using sodium uptake experiments and by the fact that tetrodotoxin did not inhibit insulin action. Because the brain Na(+)-K(+)-ATPase catalytic subunit exists as two forms with different affinities for the inhibitory cardiac glycoside ouabain, the sensitivity of each form for insulin was examined. As previously observed in adipocytes, only the high-affinity component, alpha 2, was insulin sensitive. A dose-response curve of insulin activation of the Na(+)-K(+)-ATPase demonstrated a maximal insulin effect at relatively high hormone concentrations. It is unknown, therefore, whether stimulation of the brain Na(+)-K(+)-ATPase occurs in vivo.
研究了突触体钠钾ATP酶对胰岛素的敏感性，发现在生理细胞内钠浓度存在时，该酶受激素刺激。如钠摄取实验所示，以及河豚毒素不抑制胰岛素作用这一事实表明，激活并非由钠流入囊泡介导。由于脑钠钾ATP酶催化亚基以两种对抑制性强心苷哇巴因亲和力不同的形式存在，因此研究了每种形式对胰岛素的敏感性。如先前在脂肪细胞中观察到的那样，只有高亲和力组分α2对胰岛素敏感。钠钾ATP酶的胰岛素激活剂量反应曲线表明，在相对较高的激素浓度下胰岛素作用达到最大。因此，尚不清楚脑钠钾ATP酶的刺激在体内是否会发生。
