Abstract
K+ channels in the membrane of murine pancreatic β-cells were studied using the patch-clamp technique. The delayed outward current was activated in whole-cell experiments by depolarizing voltage pulses to potentials between −30 mV and 0 mV. Forskolin blocked the current rapidly (<5 s) and reversibly with 50% inhibition at 13 μM. The inhibition did not depend on a stimulation of the adenylate cyclase since it occurred even in presence of 1 mM cAMP in the pipette solution which replaced the cytoplasm. Membrane permeant cAMP analogues and phosphodiesterase inhibitors did not influence the delayed outward current. In experiments on outside-out patches forskolin (100 μM) shortened the openings of a channel of about 10 pS conductance at 0 mV and a time course of activation and inactivation similar to the whole-cell current. Another smaller, slowly activating channel and the Ca2+- and ATP-dependent K+ channels were influenced only weakly or not at all. It is therefore concluded that the 10-pS channel generates most of the delayed outward K+ current in murine pancreatic β-cells. The Ca2+-independent part of the delayed outward current in bovine adrenal chromaffin cells was also blocked by forskolin (100 μM).
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Zünkler, B.J., Trube, G. & Ohno-Shosaku, T. Forskolin-induced block of delayed rectifying K+ channels in pancreaticβ-cells is not mediated by cAMP. Pflugers Arch. 411, 613–619 (1988). https://doi.org/10.1007/BF00580856
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DOI: https://doi.org/10.1007/BF00580856