Nielsen R
Acta Physiol Scand. 1984 Feb;120(2):287-96. doi: 10.1111/j.1748-1716.1984.tb00136.x.
In frog skin bathed in Cl--Ringer's solution the short circuit current (SCC) is equal to the net Na+ flux. In the present study Na+ and K+ transport across frog skin have been investigated in skins bathed in a solution where all Cl- has been substituted by the impermeable anion gluconate. In this solution the net Na+ flux (9.22 +/- 0.72 nmole/cm2/min) was significantly higher than the SCC (7.61 +/- 0.63) nmole/cm2/min). Measurement of the transepithelial K+ influx and K+ efflux showed that the discrepancy between the net Na+ flux and the SCC was caused by an active outwards going transepithelial K+ transport. The K+ but not the Na+ transport could be blocked by adding the K+ channel blocking agent Ba++ to the apical solution. Thus, the K+ transport occurs via a K+ specific pathway in the apical membrane. Ouabain blocked both the Na+ and the K+ transport, whereas the presence of the Na+ channel blocking agent amiloride in the apical solution blocked the Na+ transport and reduced the K+ transport. In the presence of amiloride in the apical solution the SCC and the transepithelial potential difference (PD) reversed so that the outside (the apical side) of the frog skin became positive with respect to the basolateral side. The inverted SCC was carried by an active transepithelial K+ transport, this K+ transport required the presence of Na+ in the basolateral solution. The experiments show that frog skin can insert or activate K+ channels in the apical membrane, indicating that the frog may regulate its K+ content by varying the K+ permeability of the apical membrane.
在浸浴于含氯林格氏液的蛙皮中，短路电流（SCC）等于净钠离子通量。在本研究中，已对浸浴于所有氯离子均被不可渗透阴离子葡萄糖酸盐替代的溶液中的蛙皮进行了钠离子和钾离子转运的研究。在该溶液中，净钠离子通量（9.22±0.72纳摩尔/平方厘米/分钟）显著高于短路电流（7.61±0.63）纳摩尔/平方厘米/分钟）。跨上皮钾离子内流和钾离子外流的测量表明，净钠离子通量与短路电流之间的差异是由主动外向的跨上皮钾离子转运引起的。通过向顶端溶液中添加钾离子通道阻滞剂钡离子，可以阻断钾离子而非钠离子的转运。因此，钾离子转运通过顶端膜中的钾离子特异性途径进行。哇巴因可阻断钠离子和钾离子的转运，而顶端溶液中存在钠离子通道阻滞剂氨氯吡脒时，可阻断钠离子转运并降低钾离子转运。在顶端溶液中存在氨氯吡脒时，短路电流和跨上皮电位差（PD）发生反转，使得蛙皮的外侧（顶端侧）相对于基底外侧侧变为正电位。反转的短路电流由主动跨上皮钾离子转运携带，这种钾离子转运需要基底外侧溶液中存在钠离子。实验表明，蛙皮可在顶端膜中插入或激活钾离子通道，这表明蛙可能通过改变顶端膜的钾离子通透性来调节其钾离子含量。
