Nagel W, Katz U
Physiologisches Institut, Universität München, Federal Republic of Germany.
Pflugers Arch. 1991 May;418(4):319-24. doi: 10.1007/BF00550868.
The effect of aldosterone (1 mumol/l for 4-6 h) on Na+ transport across toad skin (Bufo viridis) was studied in skins preincubated in vitro. Short-circuit current (Isc) was consistently and reproducibly elevated in skins from NaCl(100 and 200 mmol/l)-acclimated toads, where the baseline Isc was greatly reduced. The effect of aldosterone was tested in NaCl and NaNO3 Ringer's and also after oxytocin (50 mU/ml) in the latter conditions. Apical membrane conductance of the principal cells increased consistently after aldosterone in all skins and was linearly correlated with the Isc under all conditions. This confirms that the stimulation of Na+ transport originates from the effect of the aldosterone on apical Na+ channels. Basolateral membrane conductance was also significantly elevated compared with control pieces in those tissues that were preincubated with aldosterone for 4-6 h. The increase, however, did not correlate with the magnitude of the Isc. It is therefore concluded that aldosterone specifically stimulates, in addition to the apical effect, the basolateral membrane conductance. This stimulation appears to be direct and not a secondary response to the elevation of transepithelial transport rate.
在体外预孵育的蟾蜍皮肤（绿蟾蜍）中，研究了醛固酮（1 μmol/l，作用4 - 6小时）对跨蟾蜍皮肤Na⁺转运的影响。在适应了100和200 mmol/l NaCl的蟾蜍皮肤中，短路电流（Isc）持续且可重复地升高，而这些皮肤的基线Isc大幅降低。在NaCl和NaNO₃林格氏液中测试了醛固酮的作用，并且在后者条件下还测试了催产素（50 mU/ml）之后醛固酮的作用。在所有皮肤中，醛固酮作用后主细胞的顶端膜电导持续增加，并且在所有条件下都与Isc呈线性相关。这证实了Na⁺转运的刺激源于醛固酮对顶端Na⁺通道的作用。与用醛固酮预孵育4 - 6小时的对照组织相比，基底外侧膜电导也显著升高。然而，这种增加与Isc的幅度无关。因此得出结论，醛固酮除了顶端效应外，还特异性地刺激基底外侧膜电导。这种刺激似乎是直接的，而不是对跨上皮转运速率升高的次级反应。
