Bakker R, Groot J A
Am J Physiol. 1984 Feb;246(2 Pt 1):G213-7. doi: 10.1152/ajpgi.1984.246.2.G213.
We studied the effects of theophylline and ouabain on isolated intestinal mucosa of the goldfish. From continuous recordings of the intracellular potential difference, we concluded that theophylline has no considerable effect on the Cl- conductance of the apical membrane. Theophylline increased transepithelial conductance and bidirectional Cl- fluxes, while Na+ fluxes did not change appreciably. Both streaming potentials and NaCl dilution potentials were immediately reduced by theophylline. Moreover, we found a striking similarity between the effects of theophylline and ouabain. Ouabain initially increased transepithelial conductance, increased bidirectional Cl- fluxes, and instantly abolished NaCl dilution potentials. Determinations of cellular cAMP levels revealed that both theophylline and ouabain increase cAMP. The phosphodiesterase inhibitor theophylline amplified the ouabain-induced rise in cAMP, suggesting that ouabain stimulates adenylate cyclase. Since elevated extracellular K+ did not affect cAMP levels, it can be ruled out that depolarization of the cell membrane due to ouabain increases cAMP. We conclude that in this epithelium both theophylline and ouabain increase the Cl- permeability of the paracellular pathway by a cAMP-dependent mechanism.
我们研究了茶碱和哇巴因对金鱼离体肠黏膜的影响。通过对细胞内电位差的连续记录，我们得出结论：茶碱对顶端膜的氯离子电导没有显著影响。茶碱增加了跨上皮电导和双向氯离子通量，而钠离子通量没有明显变化。茶碱使流动电位和氯化钠稀释电位立即降低。此外，我们发现茶碱和哇巴因的作用之间存在显著相似性。哇巴因最初增加跨上皮电导，增加双向氯离子通量，并立即消除氯化钠稀释电位。细胞环磷酸腺苷（cAMP）水平的测定表明，茶碱和哇巴因都能增加cAMP。磷酸二酯酶抑制剂茶碱放大了哇巴因诱导的cAMP升高，表明哇巴因刺激腺苷酸环化酶。由于细胞外钾离子升高不影响cAMP水平，因此可以排除哇巴因导致的细胞膜去极化增加cAMP的可能性。我们得出结论，在这种上皮组织中，茶碱和哇巴因都通过一种依赖cAMP的机制增加细胞旁途径的氯离子通透性。
