Hinton C F, Eaton D C
Department of Physiology, Emory University Medical School, Atlanta, Georgia 30322.
Am J Physiol. 1989 Oct;257(4 Pt 1):C825-9. doi: 10.1152/ajpcell.1989.257.4.C825.
This report describes the expression of a sodium-selective, amiloride-blockable conductance in Xenopus oocytes that have been injected with RNA prepared from a distal nephron cell line (A6). After injecting the RNA into mature oocytes (stage V or VI) and incubating the oocytes for 2-4 days, the oocytes were examined for amiloride-blockable current. The RNA induced a substantial amiloride-blockable current. Uninjected or water-injected oocytes had no measurable amiloride-blockable current. RNA prepared from aldosterone-treated A6 cells was much more effective in inducing amiloride-blockable sodium current than RNA prepared from aldosterone-depleted A6 cells. Oocytes injected with RNA prepared from mineralocorticoid-depleted cells appeared very similar to water-injected oocytes. The amiloride-blockable current in oocytes has a reversal potential of approximately +50 - +60 mV, which varies 61 mV/decade change in external sodium concentration, suggesting that the current is highly selective for sodium over other ions. In addition, the concentration of amiloride that produces half block of the current is 48 +/- 8 nM. Thus the current expressed in oocytes appears very similar to sodium-selective currents observed from the apical membranes of various tight epithelial tissues.
本报告描述了在非洲爪蟾卵母细胞中一种钠选择性、氨氯地平可阻断的电导的表达情况，这些卵母细胞已注射了从远端肾单位细胞系（A6）制备的RNA。将RNA注射到成熟卵母细胞（V期或VI期）中并孵育2 - 4天后，检测卵母细胞的氨氯地平可阻断电流。该RNA诱导出大量的氨氯地平可阻断电流。未注射或注射水的卵母细胞没有可测量的氨氯地平可阻断电流。用醛固酮处理过的A6细胞制备的RNA在诱导氨氯地平可阻断的钠电流方面比用醛固酮耗竭的A6细胞制备的RNA有效得多。注射了用盐皮质激素耗竭的细胞制备的RNA的卵母细胞看起来与注射水的卵母细胞非常相似。卵母细胞中的氨氯地平可阻断电流的反转电位约为 +50 - +60 mV，随着外部钠浓度每十倍变化，该电位变化61 mV，这表明该电流对钠的选择性远高于其他离子。此外，使电流产生半数阻断的氨氯地平浓度为48 +/- 8 nM。因此，卵母细胞中表达的电流看起来与在各种紧密上皮组织的顶端膜上观察到的钠选择性电流非常相似。
