Gunter-Smith P J, White J F
Am J Physiol. 1979 Jun;236(6):E775-83. doi: 10.1152/ajpendo.1979.236.6.E775.
The electrolyte transport properties of isolated proximal segments of Amphiuma small intestine and their response to theophylline were observed under various conditions. In the absence of theophylline the intestine generates a transepithelial potential (psi ms) serosa negative to mucosa when Cl- and HCO3- are present in the bath. Replacement of Cl- or HCO3- reduced the magnitude and usually reversed the sign of psi ms. Acetazolamide (10(-4) M) nearly abolished the serosa negative psi ms. Theophylline (10 mM) drove psi ms serosa positive, the magnitude depending on the bath Na+ and HCO3- concentrations. Simultaneously it increased the short-circuit current (Isc) and tissue resistance (Rt). The increase in Isc was not due to increase net Na+ transport in Cl-free buffer and was attributed to a residual ion flux. Acetazolamide reduced the Isc, Rt, and the net residual flux observed in theophylline-treated intestine. The magnitude of the acetazolamine effect on Isc was proportional to the Na+ and HCO3- concentrations of the bath. The results suggest that in the absence of theophylline, HCO3-, and Cl- transport are related. Furthermore, acetazolamide inhibits the movement of an ion, possibly HCO3-, secreted in response to theophylline.
在不同条件下观察了蚓螈小肠分离近端节段的电解质转运特性及其对茶碱的反应。在无茶碱的情况下，当浴液中存在Cl⁻和HCO₃⁻时，小肠产生跨上皮电位（ψms），浆膜相对于黏膜呈负性。用Cl⁻或HCO₃⁻替代会降低ψms的幅度，且通常会使ψms的正负号反转。乙酰唑胺（10⁻⁴M）几乎消除了浆膜负性的ψms。茶碱（10mM）使ψms变为浆膜正性，其幅度取决于浴液中Na⁺和HCO₃⁻的浓度。同时，它增加了短路电流（Isc）和组织电阻（Rt）。在无Cl⁻缓冲液中，Isc的增加并非由于净Na⁺转运增加，而是归因于残余离子通量。乙酰唑胺降低了在茶碱处理的小肠中观察到的Isc、Rt和净残余通量。乙酰唑胺对Isc的作用幅度与浴液中Na⁺和HCO₃⁻的浓度成正比。结果表明，在无茶碱的情况下，HCO₃⁻和Cl⁻的转运相关。此外，乙酰唑胺抑制了因茶碱刺激而分泌的一种离子（可能是HCO₃⁻）的移动。
