Abstract
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.
Full text
PDFSelected References
These references are in PubMed. This may not be the complete list of references from this article.
- ARMSTRONG C. M., BINSTOCK L. ANOMALOUS RECTIFICATION IN THE SQUID GIANT AXON INJECTED WITH TETRAETHYLAMMONIUM CHLORIDE. J Gen Physiol. 1965 May;48:859–872. doi: 10.1085/jgp.48.5.859. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ehrenstein G., Lecar H., Nossal R. The nature of the negative resistance in bimolecular lipid membranes containing excitability-inducing material. J Gen Physiol. 1970 Jan;55(1):119–133. doi: 10.1085/jgp.55.1.119. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eipper B. A., Mains R. E. Structure and biosynthesis of pro-adrenocorticotropin/endorphin and related peptides. Endocr Rev. 1980 Winter;1(1):1–27. doi: 10.1210/edrv-1-1-1. [DOI] [PubMed] [Google Scholar]
- Gorman A. L., Thomas M. V. Potassium conductance and internal calcium accumulation in a molluscan neurone. J Physiol. 1980 Nov;308:287–313. doi: 10.1113/jphysiol.1980.sp013472. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
- Hermann A., Gorman A. L. Effects of tetraethylammonium on potassium currents in a molluscan neurons. J Gen Physiol. 1981 Jul;78(1):87–110. doi: 10.1085/jgp.78.1.87. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Horn R., Patlak J. Single channel currents from excised patches of muscle membrane. Proc Natl Acad Sci U S A. 1980 Nov;77(11):6930–6934. doi: 10.1073/pnas.77.11.6930. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Latorre R., Vergara C., Hidalgo C. Reconstitution in planar lipid bilayers of a Ca2+-dependent K+ channel from transverse tubule membranes isolated from rabbit skeletal muscle. Proc Natl Acad Sci U S A. 1982 Feb;79(3):805–809. doi: 10.1073/pnas.79.3.805. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lecar H., Ehrenstein G., Latorre R. Mechanism for channel gating in excitable bilayers. Ann N Y Acad Sci. 1975 Dec 30;264:304–313. doi: 10.1111/j.1749-6632.1975.tb31491.x. [DOI] [PubMed] [Google Scholar]
- Lux H. D., Neher E., Marty A. Single channel activity associated with the calcium dependent outward current in Helix pomatia. Pflugers Arch. 1981 Mar;389(3):293–295. doi: 10.1007/BF00584792. [DOI] [PubMed] [Google Scholar]
- Marty A. Ca-dependent K channels with large unitary conductance in chromaffin cell membranes. Nature. 1981 Jun 11;291(5815):497–500. doi: 10.1038/291497a0. [DOI] [PubMed] [Google Scholar]
- Meech R. W. Intracellular calcium injection causes increased potassium conductance in Aplysia nerve cells. Comp Biochem Physiol A Comp Physiol. 1972 Jun 1;42(2):493–499. doi: 10.1016/0300-9629(72)90128-4. [DOI] [PubMed] [Google Scholar]
- Meech R. W. The sensitivity of Helix aspersa neurones to injected calcium ions. J Physiol. 1974 Mar;237(2):259–277. doi: 10.1113/jphysiol.1974.sp010481. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Meech R. W., Thomas R. C. Effect of measured calcium chloride injections on the membrane potential and internal pH of snail neurones. J Physiol. 1980 Jan;298:111–129. doi: 10.1113/jphysiol.1980.sp013070. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Neher E., Sakmann B., Steinbach J. H. The extracellular patch clamp: a method for resolving currents through individual open channels in biological membranes. Pflugers Arch. 1978 Jul 18;375(2):219–228. doi: 10.1007/BF00584247. [DOI] [PubMed] [Google Scholar]
- Pallotta B. S., Magleby K. L., Barrett J. N. Single channel recordings of Ca2+-activated K+ currents in rat muscle cell culture. Nature. 1981 Oct 8;293(5832):471–474. doi: 10.1038/293471a0. [DOI] [PubMed] [Google Scholar]
- Sigworth F. J., Neher E. Single Na+ channel currents observed in cultured rat muscle cells. Nature. 1980 Oct 2;287(5781):447–449. doi: 10.1038/287447a0. [DOI] [PubMed] [Google Scholar]
- Yasumura Y. Retention of differentiated function in clonal animal cell lines, particularly hormone-secreting cultures. Am Zool. 1968 May;8(2):285–305. doi: 10.1093/icb/8.2.285. [DOI] [PubMed] [Google Scholar]