Haag K, Lübcke R, Knauf H, Berger E, Gerok W
Pflugers Arch. 1985;405 Suppl 1:S67-70. doi: 10.1007/BF00581782.
A direct clamping technique is demonstrated, which allows monitoring of rapid changes of the short-circuit current (Isc) and the specific transepithelial resistance (Rm) as well as measurement of ion fluxes under short-circuit conditions in vivo. Due to the cylindrical symmetry of the colon the intraluminal electrode was devised as a centrally fixed silver rod, by which radial current injection was achieved. The geometrical arrangement of the electrodes guaranteed zero potential difference (PD) along the whole axis of the colon segment. The Isc was determined to 3.3 +/- 0.7 mueq h-1 cm-2 and Rm equal to 121 +/- 5 omega cm2. These data obtained by direct short-circuiting agree well with our earlier Rm and Isc data based on cable analysis, where the Isc was calculated from the open-circuit PD and Rm. This is considered as evidence for the reliability of the two independent in vivo techniques. Their validity was confirmed by the expected effects of drugs acting on rheogenic ion transport. Both the indirect (via Rm) as well as the direct Isc determination may be used alternatively as required; one may serve to match the other. For larger tubular structures like the rat colon the direct clamping should be preferred as the standard procedure for the Isc determination in vivo.
本文展示了一种直接钳夹技术，该技术可用于监测短路电流（Isc）和比跨上皮电阻（Rm）的快速变化，以及在体内短路条件下测量离子通量。由于结肠的圆柱对称性，腔内电极被设计为中心固定的银棒，通过它可以实现径向电流注入。电极的几何排列确保了沿结肠段整个轴的零电位差（PD）。测得Isc为3.3±0.7μeq h-1 cm-2，Rm为121±5Ω cm2。通过直接短路获得的这些数据与我们早期基于电缆分析的Rm和Isc数据非常吻合，其中Isc是根据开路PD和Rm计算得出的。这被视为这两种独立体内技术可靠性的证据。作用于生电离子转运的药物的预期效果证实了它们的有效性。间接（通过Rm）以及直接Isc测定都可根据需要交替使用；一种方法可用于验证另一种方法。对于像大鼠结肠这样较大的管状结构，直接钳夹应作为体内Isc测定的标准方法优先选用。
