Abstract
High-conductance Ca(2+)-activated K+ channels from rat skeletal muscle were incorporated into planar lipid bilayers, and the channel kinetics were studied with a high internal Ca2+ concentration (Cai). Raising the Cai is known to increase the channel open probability. This effect is due to an increases in openings frequency and duration, and saturates at a Cai around 100 microM. Raising the Cai also increases the occurrence of less frequent but very long (> 5 s) shut events. The mechanism underlying this slow kinetic process was studied. Raising Cai above 100 microM does not further increase the frequency of the long shut events. This was not consistent with the hypothesis that the long closures result from a classical channel-block mechanism induced by internal Ca2+. The transmembrane voltage and the presence of K+ ions in the external compartment both affect the slow kinetic process. A comparison of these effects with the properties of the channel block induced by Ba2+ ions added to the internal compartment strongly suggested that the long shut events are due to a contamination of the internal solutions by Ba2+. This was confirmed by showing that a crown-ether compound that strongly chelates Ba2+ completely suppresses the long shut events when added to the inner compartment.
Full text
PDF






Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Armstrong C. M., Swenson R. P., Jr, Taylor S. R. Block of squid axon K channels by internally and externally applied barium ions. J Gen Physiol. 1982 Nov;80(5):663–682. doi: 10.1085/jgp.80.5.663. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Armstrong C. M., Taylor S. R. Interaction of barium ions with potassium channels in squid giant axons. Biophys J. 1980 Jun;30(3):473–488. doi: 10.1016/S0006-3495(80)85108-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Barrett J. N., Magleby K. L., Pallotta B. S. Properties of single calcium-activated potassium channels in cultured rat muscle. J Physiol. 1982 Oct;331:211–230. doi: 10.1113/jphysiol.1982.sp014370. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Benham C. D., Bolton T. B., Lang R. J., Takewaki T. The mechanism of action of Ba2+ and TEA on single Ca2+-activated K+ -channels in arterial and intestinal smooth muscle cell membranes. Pflugers Arch. 1985 Feb;403(2):120–127. doi: 10.1007/BF00584088. [DOI] [PubMed] [Google Scholar]
- Copello J., Simon B., Segal Y., Wehner F., Ramanujam V. M., Alcock N., Reuss L. Ba2+ release from soda glass modifies single maxi K+ channel activity in patch clamp experiments. Biophys J. 1991 Oct;60(4):931–941. doi: 10.1016/S0006-3495(91)82127-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Diaz F., Wallner M., Stefani E., Toro L., Latorre R. Interaction of internal Ba2+ with a cloned Ca(2+)-dependent K+ (hslo) channel from smooth muscle. J Gen Physiol. 1996 Mar;107(3):399–407. doi: 10.1085/jgp.107.3.399. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eaton D. C., Brodwick M. S. Effects of barium on the potassium conductance of squid axon. J Gen Physiol. 1980 Jun;75(6):727–750. doi: 10.1085/jgp.75.6.727. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ferguson W. B. Competitive Mg2+ block of a large-conductance, Ca(2+)-activated K+ channel in rat skeletal muscle. Ca2+, Sr2+, and Ni2+ also block. J Gen Physiol. 1991 Jul;98(1):163–181. doi: 10.1085/jgp.98.1.163. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Findlay I., Dunne M. J., Petersen O. H. High-conductance K+ channel in pancreatic islet cells can be activated and inactivated by internal calcium. J Membr Biol. 1985;83(1-2):169–175. doi: 10.1007/BF01868748. [DOI] [PubMed] [Google Scholar]
- Hanke W., Miller C. Single chloride channels from Torpedo electroplax. Activation by protons. J Gen Physiol. 1983 Jul;82(1):25–45. doi: 10.1085/jgp.82.1.25. [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]
- Magleby K. L., Pallotta B. S. Calcium dependence of open and shut interval distributions from calcium-activated potassium channels in cultured rat muscle. J Physiol. 1983 Nov;344:585–604. doi: 10.1113/jphysiol.1983.sp014957. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Marty A. Blocking of large unitary calcium-dependent potassium currents by internal sodium ions. Pflugers Arch. 1983 Feb;396(2):179–181. doi: 10.1007/BF00615524. [DOI] [PubMed] [Google Scholar]
- Marty A., Tan Y. P., Trautmann A. Three types of calcium-dependent channel in rat lacrimal glands. J Physiol. 1984 Dec;357:293–325. doi: 10.1113/jphysiol.1984.sp015501. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Methfessel C., Boheim G. The gating of single calcium-dependent potassium channels is described by an activation/blockade mechanism. Biophys Struct Mech. 1982;9(1):35–60. doi: 10.1007/BF00536014. [DOI] [PubMed] [Google Scholar]
- Miller C., Latorre R., Reisin I. Coupling of voltage-dependent gating and Ba++ block in the high-conductance, Ca++-activated K+ channel. J Gen Physiol. 1987 Sep;90(3):427–449. doi: 10.1085/jgp.90.3.427. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Moczydlowski E. G., Latorre R. Saxitoxin and ouabain binding activity of isolated skeletal muscle membrane as indicators of surface origin and purity. Biochim Biophys Acta. 1983 Jul 27;732(2):412–420. doi: 10.1016/0005-2736(83)90058-5. [DOI] [PubMed] [Google Scholar]
- Moczydlowski E., Latorre R. Gating kinetics of Ca2+-activated K+ channels from rat muscle incorporated into planar lipid bilayers. Evidence for two voltage-dependent Ca2+ binding reactions. J Gen Physiol. 1983 Oct;82(4):511–542. doi: 10.1085/jgp.82.4.511. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Neyton J., Miller C. Potassium blocks barium permeation through a calcium-activated potassium channel. J Gen Physiol. 1988 Nov;92(5):549–567. doi: 10.1085/jgp.92.5.549. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Neyton J., Pelleschi M. Multi-ion occupancy alters gating in high-conductance, Ca(2+)-activated K+ channels. J Gen Physiol. 1991 Apr;97(4):641–665. doi: 10.1085/jgp.97.4.641. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Oberhauser A., Alvarez O., Latorre R. Activation by divalent cations of a Ca2+-activated K+ channel from skeletal muscle membrane. J Gen Physiol. 1988 Jul;92(1):67–86. doi: 10.1085/jgp.92.1.67. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pallotta B. S. Calcium-activated potassium channels in rat muscle inactivate from a short-duration open state. J Physiol. 1985 Jun;363:501–516. doi: 10.1113/jphysiol.1985.sp015724. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Vergara C., Latorre R. Kinetics of Ca2+-activated K+ channels from rabbit muscle incorporated into planar bilayers. Evidence for a Ca2+ and Ba2+ blockade. J Gen Physiol. 1983 Oct;82(4):543–568. doi: 10.1085/jgp.82.4.543. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Yellen G. Ionic permeation and blockade in Ca2+-activated K+ channels of bovine chromaffin cells. J Gen Physiol. 1984 Aug;84(2):157–186. doi: 10.1085/jgp.84.2.157. [DOI] [PMC free article] [PubMed] [Google Scholar]