Single calcium-dependent potassium channels in clonal anterior pituitary cells.
Single Ca2+-dependent K+-channel currents were recorded in intact and excised inside-out membrane patches of the anterior pituitary clone AtT-20/D16-16. The frequency of channel openings and lifetimes depends both on membrane potential and on the Ca2+ concentrations at the inner membrane surface. The curve of the open-state probability of the channel as a function of membrane potential appears to translate along the voltage axis with changes in internal Ca2+ concentration. For Ca2+ concentrations between 10(-7) and 10(-6) M, the shift is consistent with the hypothesis that three Ca2+ ions are required to open a Ca2+-dependent K+ channel. Single channel conductances are estimated to be 124 pS in patches with normal external K+ (5.4 mM) and 208 pS in excised patches with symmetrical K+ (145 mM) across the membrane. Tetraethylammonium (20 mM) added to the cytoplasmic surface reversibly blocks the Ca2+-dependent K+ channel.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000502:physiology; D002999:Clone Cells; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D010903:Pituitary Gland, Anterior / Q000503:physiopathology*; D010911:Pituitary Neoplasms / Q000503:physiopathology*; D011188:Potassium / Q000378:metabolism*
D007473:Ion Channels; D011188:Potassium; D002118:Calcium