Macknight A D, Civan M M, Leaf A
J Membr Biol. 1975;20(3-4):387-401. doi: 10.1007/BF01870645.
Transepithelial sodium transport was virtually abolished when toad urinary hemibladders, mounted in chambers and short-circuited, were exposed on their serosal surface to ouabain, 10-2 M,for 60 minutes. Epithelial cells scraped from such hemibladders gained sodium and lost an equal quantity of potassium when compared with controls not exposed to cardiac glycoside. Their total cellular cation content, chloride content and water content were unchanged. Experiments in which 24-Na, amiloride, or sodium-free mucosal solutions were used, revealed that a large, though variable, percentage of the sodium gained by cells exposed to oubain, came from the mucosal medium, a finding consistent with the model of passive sodium entry from the mucosal medium followed by active sodium extrusion to the serosa. The oubain-insensitive maintenance of cellular volume which was observed did not depend upon transepithelial sodium transport which had been virtually completely inhibited by ouabain. Neither did the maintenance of a normal cellular potassium content depend upon transepithelial sodium transport, for cellular potassium was unaffected when the mucosal medium was sodium-free or when it contained sufficient amiloride, 10-3 M, to virtually abolish such transport.
将蟾蜍的尿半膀胱置于小室中并进行短路处理，当浆膜表面暴露于10⁻²M的哇巴因60分钟时，跨上皮钠转运实际上被消除。与未暴露于强心苷的对照组相比，从这种半膀胱刮下的上皮细胞摄取了钠并失去了等量的钾。它们的总细胞阳离子含量、氯含量和水含量没有变化。使用²⁴Na、氨氯吡脒或无钠黏膜溶液的实验表明，暴露于哇巴因的细胞摄取的钠中，有很大比例（尽管可变）来自黏膜介质，这一发现与钠从黏膜介质被动进入然后主动向浆膜挤出的模型一致。观察到的细胞体积对哇巴因不敏感的维持并不依赖于已被哇巴因几乎完全抑制的跨上皮钠转运。正常细胞钾含量的维持也不依赖于跨上皮钠转运，因为当黏膜介质无钠或含有足够的氨氯吡脒（10⁻³M）以几乎消除这种转运时，细胞钾不受影响。
