Separate Cl- conductances activated by cAMP and Ca2+ in Cl(-)-secreting epithelial cells.

作者：William H. Cliff, Raymond A. Frizzell · 发表于：Proceedings of the National Academy of Sciences · 年份：1990 · DOI：10.1073/pnas.87.13.4956 · 被引用次数：356 · 研究领域：Ion channel regulation and function、Neuroscience and Neuropharmacology Research、Cardiac electrophysiology and arrhythmias

We studied the cAMP- and Ca2(+)-activated secretory Cl- conductances in the Cl(-)-secreting colonic epithelial cell line T84 using the whole-cell patch-clamp technique. Cl- and K+ currents were measured under voltage clamp. Forskolin or cAMP increased Cl- current 2-15 times with no change in K+ current. The current-voltage relation for cAMP-activated Cl- current was linear from -100 to +100 mV and showed no time-dependent changes in current during voltage pulses. Ca2+ ionophores or increased pipette Ca2+ increased both Cl- and K+ currents 2-30 times. The Ca2(+)-activated Cl- current was outwardly rectified, activated during depolarizing voltage pulses, and inactivated during hyperpolarizing voltage pulses. Addition of ionophore after forskolin further increased Cl- conductance 1.5-5 times, and the current took on the time-dependent characteristics of that stimulated by Ca2+. Thus, cAMP and Ca2+ activate Cl- conductances with different properties, implying that these second messengers activate different Cl- channels or that they induce different conductive and kinetic states in the same Cl- channel.