Gordon L G
J Membr Biol. 1978 Dec 29;44(3-4):309-19. doi: 10.1007/BF01944226.
Toad urinary bladders were mounted in Ussing-type chambers and volt-age-clamped. At nonzero voltages only, small fluctuations in current, delta I, and therefore in tissue conductance, delta Gt, were detected. These fluctuations were caused by the smooth muscle of the underlying tissue which could be monitored continuously and simultaneously with the current, I. Inhibition of the smooth muscle contraction with verapamil (2 X 10(-5) M) abolished the fluctuations in I and Gt. Amiloride (10(-4) M) had no significant effect on the magnitude of delta Gt, oxytocin increased Gt without affecting delta Gt, and mucosal hypertonicity produced by mannitol increased delta Gt. These results are consistent with the hypothesis that two parallel pathways exist for passive current flow across the toad urinary bladder: one, the cellular pathway, was not affected by smooth muscle activity; the other, the paracellular pathway, was the route whose conductance was altered by the action of the smooth muscle. Thus the relationship between the cellular and shunt conductances of the epithelium of the toad urinary bladder, under a variety of conditions, can be investigated by utilizing the effects of the movement of the smooth muscle.
将蟾蜍膀胱安装在尤斯灌流小室中并进行电压钳制。仅在非零电压下，检测到电流的微小波动（δI），进而检测到组织电导的微小波动（δGt）。这些波动是由下层组织的平滑肌引起的，可与电流I同时持续监测。用维拉帕米（2×10⁻⁵ M）抑制平滑肌收缩消除了I和Gt的波动。氨氯吡脒（10⁻⁴ M）对δGt的幅度无显著影响，催产素增加了Gt但不影响δGt，甘露醇产生的黏膜高渗性增加了δGt。这些结果与以下假设一致：蟾蜍膀胱存在两条平行的被动电流跨膜通路：一条是细胞通路，不受平滑肌活动影响；另一条是细胞旁通路，其电导受平滑肌作用改变。因此，利用平滑肌运动的影响，可以研究蟾蜍膀胱上皮细胞电导和旁路电导在各种条件下的关系。
