Lyall V, Belcher T S, Miller J H, Biber T U
Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0551.
Am J Physiol. 1994 Jul;267(1 Pt 2):R107-14. doi: 10.1152/ajpregu.1994.267.1.R107.
Intracellular pH (pHi), apical membrane potential (Va), and fractional apical membrane resistance (FRa) were measured in principal cells of isolated frog skin (Rana pipiens) with double-barreled microelectrodes under short-circuit conditions. Basolateral exposure to 10 mU/ml arginine vasotocin (AVT) depolarized Va by 30 mV, decreased FRa by 33%, increased short-circuit current (Isc) by 17 microA, and increased pHi by 0.17 pH units. The response of Va, Isc, and pHi occurred concurrently. Forskolin, theophylline, and 8-(4-chlorophenyl-thio)-adenosine 3',5'-cyclic monophosphate caused similar changes in Va, Isc, and pHi. The enhanced response of Isc, Va, and FRa to short pulses of apical amiloride applied during AVT or cAMP exposure suggests an increase in apical Na+ conductance. The presence of cAMP agonists also enhanced the response of pHi to amiloride. We conclude that the AVT- and cAMP-induced increase in Na+ transport across the apical cell membrane is associated with a change in pHi. These data are consistent with the hypothesis that changes in pHi may play a role in the second messenger cascade initiated by the antidiuretic hormone.
在短路条件下，使用双管微电极在分离的蛙皮（豹蛙）主细胞中测量细胞内pH值（pHi）、顶端膜电位（Va）和顶端膜电阻分数（FRa）。基底外侧暴露于10 mU/ml精氨酸血管加压素（AVT）使Va去极化30 mV，使FRa降低33%，使短路电流（Isc）增加17 μA，并使pHi增加0.17个pH单位。Va、Isc和pHi的反应同时发生。福斯可林、茶碱和8-（4-氯苯基硫代）-腺苷3',5'-环磷酸引起Va、Isc和pHi的类似变化。在AVT或cAMP暴露期间，Isc、Va和FRa对顶端应用的短脉冲阿米洛利的增强反应表明顶端Na+电导增加。cAMP激动剂的存在也增强了pHi对阿米洛利的反应。我们得出结论，AVT和cAMP诱导的跨顶端细胞膜的Na+转运增加与pHi的变化有关。这些数据与pHi变化可能在抗利尿激素引发的第二信使级联反应中起作用的假设一致。
