Renfro J L, Miller D S, Karnaky K J, Kinter W B
Am J Physiol. 1976 Dec;231(6):1735-43. doi: 10.1152/ajplegacy.1976.231.6.1735.
Previous studies on the urinary bladder of the seawater-acclimated winter flounder (pseudopleuronectes americanus) demonstrated that active Na and Cl transport were ouabain sensitive. This suggested a relationship between the Na pump and Na-K-ATP-ase. The specific binding of [H]ouabain to Na-K-ATPase provides a means of localizing the site of active Na transport. In isolated bladders, a positive linear correlation (r= 0.89) was found between the active Na transport rate and the Na-K-ATPase activity. Ouabain binding by the bladder surface appeared to be saturable and relatively specific, e.g., was reduced by a high K concentration. When only the mucosal side of the bladder was exposed to 5 muM ouabain, both inhibitory effects and binding were small and are explained by finite permeability of the bladder to ouabain. In contrast, binding and inhibitory effects from the serosal side were much greater. Autoradiographs demonstrated that [3H]ouabain was bound only to the serosal side of the epithelial cells. Ultrastructural examination revealed that the area of ouabain binding coincided with the basal and lateral plasma membranes.
先前对适应海水的美洲拟鲽膀胱的研究表明，活跃的钠和氯转运对哇巴因敏感。这表明钠泵与钠钾ATP酶之间存在关联。[H]哇巴因与钠钾ATP酶的特异性结合提供了一种定位活跃钠转运位点的方法。在分离的膀胱中，活跃钠转运速率与钠钾ATP酶活性之间存在正线性相关（r = 0.89）。膀胱表面对哇巴因的结合似乎是可饱和的且相对特异，例如，高钾浓度会使其降低。当仅将膀胱的黏膜侧暴露于5 μM哇巴因时，抑制作用和结合都很小，这可通过膀胱对哇巴因的有限通透性来解释。相比之下，来自浆膜侧的结合和抑制作用要大得多。放射自显影片显示，[3H]哇巴因仅结合于上皮细胞的浆膜侧。超微结构检查表明，哇巴因结合区域与基底和侧质膜重合。
