Macchia D D, Helman S I
Biophys J. 1979 Sep;27(3):371-92. doi: 10.1016/S0006-3495(79)85224-8.
Studies were done to investigate the transepithelial current-voltage (IT-VT) relationships of urinary bladder and colon of the toad Bufo marinus. Like several other Na transporting epithelia, the IT-VT plots characteristically showed a break at voltage E1, averaging near 124 mV for urinary bladder and 110 mV for colon. With bladders treated with antidiuretic hormone, estimates of ENa and shunt resistance, Rs, were obtained according to a method outlined by Yonath and Civan, 1971 (J Membr. Biol. 5:336-385). Our results not only confirmed their observations, but were consistent with the notion that the values of E1 (IT-VT plots) were the same as those of ENa. In addition, the values of Rs were found to be the same as those estimated from the quotient E1/I1 obtained from the voltage and current coordinates at the break of the IT-VT plot of bladders studied in both stretched and unstretched states. Amiloride at concentrations up to 10(-5) M caused a small decrease of both E1 and E1/I1 of urinary bladder. Similarly, amiloride caused small but significant changes of ENa and RNa of the colon. For both epithelia, the values of E1 and E1/I1 of the IT-VT plots were the same as those of ENa and Rs estimated by an independent method. In general, these findings are similar to those of several other epithelia where the ENa and Rs can be estimated directly from their IT-VT relationships.
开展了多项研究以探究海蟾蜍膀胱和结肠的跨上皮电流-电压（IT-VT）关系。与其他几种转运钠离子的上皮组织一样，IT-VT图的特征是在电压E1处出现转折，膀胱的E1平均接近124 mV，结肠的E1平均接近110 mV。对于用抗利尿激素处理过的膀胱，根据Yonath和Civan在1971年概述的方法（《膜生物学杂志》5:336 - 385）获得了ENa和分流电阻Rs的估计值。我们的结果不仅证实了他们的观察结果，而且与E1（IT-VT图）的值与ENa的值相同这一观点一致。此外，发现Rs的值与从拉伸和未拉伸状态下研究的膀胱的IT-VT图转折处的电压和电流坐标获得的商E1/I1估计的值相同。浓度高达10(-5) M的氨氯吡脒导致膀胱的E1和E1/I1均略有下降。同样，氨氯吡脒引起结肠的ENa和RNa有小但显著的变化。对于这两种上皮组织，IT-VT图的E1和E1/I1的值与通过独立方法估计的ENa和Rs的值相同。总体而言，这些发现与其他几种上皮组织的发现相似，在这些上皮组织中，可以直接从它们的IT-VT关系估计ENa和Rs。
