Van Driessche W
Laboratorium voor Fysiologie, KUL, Campus Gasthuisberg, Leuven, Belgium.
Pflugers Arch. 1987 Oct;410(3):243-9. doi: 10.1007/BF00580272.
Previously (Van Driessche et al. 1987) we showed that small inward (mucosa towards serosa) oriented short-circuit currents (Isc) were recorded through the toad urinary bladder when the mucosal side was exposed to Ca2+ free solutions containing K+, Na+ (+ amiloride), Cs+ or Rb+ as main cation. This current component is inhibitable by micromolar concentrations of mucosal La3+ and divalent cations (Ca2+, Cd2+) and is considerably elevated by oxytocin (0.1 U/ml). The present study demonstrates that the addition of 50 nmol/l Ag+ to the mucosal medium during oxytocin treatment caused an additional large increase of the La3+-sensitive Isc component. The power density spectrum of the fluctuation in current contained a Lorentzian component which was enhanced by oxytocin treatment. The Lorentzian component disappeared as a consequence of the administration of mucosal Ag+. In experiments with Ca2+, Ba2+ or Mg2+ as principal mucosal cation, the La3+-sensitive Isc component was negligible under control conditions and during oxytocin treatment. Mucosal Ag+ (40 nmol/l) elicited a large inward oriented current which was blockable by the calcium channel blockers, La3+ and Cd2+. Also the organic calcium entry blockers, nicardipine and verapamil (10 mumol/l) depressed the inward current considerably. Noise analysis of the currents carried by divalent cations showed a La3+-sensitive noise component. Oxytocin-Ag+ activated currents could not be recorded in the absence of the divalent cations or small inorganic cations, e.g. with solutions which contained N-methyl D-glucamine (NMDG) as main mucosal cation.
此前（Van Driessche等人，1987年）我们发现，当蟾蜍膀胱黏膜侧暴露于以K⁺、Na⁺（+氨氯吡脒）、Cs⁺或Rb⁺作为主要阳离子的无Ca²⁺溶液中时，会记录到小的内向（从黏膜向浆膜）定向短路电流（Isc）。该电流成分可被微摩尔浓度的黏膜La³⁺和二价阳离子（Ca²⁺、Cd²⁺）抑制，并可被催产素（0.1 U/ml）显著增强。本研究表明，在催产素处理期间向黏膜介质中添加50 nmol/l Ag⁺会导致La³⁺敏感的Isc成分进一步大幅增加。电流波动的功率密度谱包含一个洛伦兹成分，该成分在催产素处理后增强。由于给予黏膜Ag⁺，洛伦兹成分消失。在以Ca²⁺、Ba²⁺或Mg²⁺作为主要黏膜阳离子的实验中，在对照条件下和催产素处理期间，La³⁺敏感的Isc成分可忽略不计。黏膜Ag⁺（40 nmol/l）引发一个大的内向电流，该电流可被钙通道阻滞剂La³⁺和Cd²⁺阻断。有机钙内流阻滞剂尼卡地平和平维拉帕米（10 μmol/l）也可显著抑制内向电流。对二价阳离子携带的电流进行噪声分析显示存在一个La³⁺敏感的噪声成分。在没有二价阳离子或小的无机阳离子的情况下，例如使用以N - 甲基 - D - 葡糖胺（NMDG）作为主要黏膜阳离子的溶液时，无法记录到催产素 - Ag⁺激活的电流。
