Skip to main content
PMC home page
The Journal of Physiology logoLink to The Journal of Physiology
. 1988 Dec;407:311–328. doi: 10.1113/jphysiol.1988.sp017417

A study of stretch-activated channels in the membrane of frog oocytes: interactions with Ca2+ ions.

V Taglietti 1, M Toselli 1
PMCID: PMC1191205  PMID: 2476552

Abstract

1. We have carried out patch-clamp measurements on a cationic channel in the plasma membrane of the frog oocyte, which can be specifically activated by membrane stretch. The kinetics of this channel also display a distinct dependence upon membrane potential, the probability of the channel being open increasing with membrane depolarization. 2. When the patch-clamp pipette filling solution was standard Ringer solution, the single-channel current-voltage (I-V) relationship was linear, the elementary conductance being 38 pS and the reversal potential +7 mV, suggesting very poor selectivity of the channel for the various cations. 3. The I-V relationship was highly non-linear having a strong inward-going rectification when Ca2+-free solutions were used to fill the patch pipette. These solutions also resulted in a selective, inward cationic permeability through the membrane, with K+ being more permeable than Na+ greater than Li+ greater than Ba2+ greater than Ca2+. 4. Though permeant through the stretch-activated channel, Ca2+ inhibited in a concentration-dependent manner the currents carried by other cations. La3+ (0.1 mM) was also an effective channel blocker. 5. The inward current carried by individual cations at a given membrane potential increased with increasing external cation concentration up to a saturating level, this level being maximal for K+ and minimal for Ca2+. Also the half-saturating concentration was maximal for K+ and minimal for Ca2+ at all membrane potentials. 6. In the presence of a constant Ca2+ concentration (50 microM) increasing [K+] did not change the absolute level at which the current saturated; however the half-saturating K+ concentration was greatly increased, indicating competitive inhibition between Ca2+ and K+ for the same site. 7. The data are consistent with a model based on Eyring rate theory for current conduction through ionic channels, in which we assume that the ions capable of entering the channel compete for a binding site that they must first occupy before proceeding on. The possible energy profile of the stretch-activated channel was defined by optimizing the model parameters to obtain the best fit of the experimental data. Ca2+ was found to have a smaller dissociation constant and much longer occupancy time than Na+ or K+, thus accounting for its lower permeability and inhibitory effect on current conduction by other cations through the stretch-activatable channel.

Full text

PDF

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Almers W., McCleskey E. W. Non-selective conductance in calcium channels of frog muscle: calcium selectivity in a single-file pore. J Physiol. 1984 Aug;353:585–608. doi: 10.1113/jphysiol.1984.sp015352. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Bezanilla F. A high capacity data recording device based on a digital audio processor and a video cassette recorder. Biophys J. 1985 Mar;47(3):437–441. doi: 10.1016/S0006-3495(85)83935-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Cooper K. E., Tang J. M., Rae J. L., Eisenberg R. S. A cation channel in frog lens epithelia responsive to pressure and calcium. J Membr Biol. 1986;93(3):259–269. doi: 10.1007/BF01871180. [DOI] [PubMed] [Google Scholar]
  4. Dumont J. N. Oogenesis in Xenopus laevis (Daudin). I. Stages of oocyte development in laboratory maintained animals. J Morphol. 1972 Feb;136(2):153–179. doi: 10.1002/jmor.1051360203. [DOI] [PubMed] [Google Scholar]
  5. Eisenman G., Horn R. Ionic selectivity revisited: the role of kinetic and equilibrium processes in ion permeation through channels. J Membr Biol. 1983;76(3):197–225. doi: 10.1007/BF01870364. [DOI] [PubMed] [Google Scholar]
  6. FATT P., GINSBORG B. L. The ionic requirements for the production of action potentials in crustacean muscle fibres. J Physiol. 1958 Aug 6;142(3):516–543. doi: 10.1113/jphysiol.1958.sp006034. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Guharay F., Sachs F. Mechanotransducer ion channels in chick skeletal muscle: the effects of extracellular pH. J Physiol. 1985 Jun;363:119–134. doi: 10.1113/jphysiol.1985.sp015699. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Guharay F., Sachs F. Stretch-activated single ion channel currents in tissue-cultured embryonic chick skeletal muscle. J Physiol. 1984 Jul;352:685–701. doi: 10.1113/jphysiol.1984.sp015317. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. 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]
  10. Hille B. Ionic selectivity of Na and K channels of nerve membranes. Membranes. 1975;3:255–323. [PubMed] [Google Scholar]
  11. Kusano K., Miledi R., Stinnakre J. Cholinergic and catecholaminergic receptors in the Xenopus oocyte membrane. J Physiol. 1982 Jul;328:143–170. doi: 10.1113/jphysiol.1982.sp014257. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Lansman J. B., Hallam T. J., Rink T. J. Single stretch-activated ion channels in vascular endothelial cells as mechanotransducers? 1987 Feb 26-Mar 4Nature. 325(6107):811–813. doi: 10.1038/325811a0. [DOI] [PubMed] [Google Scholar]
  13. Lewis C. A. Ion-concentration dependence of the reversal potential and the single channel conductance of ion channels at the frog neuromuscular junction. J Physiol. 1979 Jan;286:417–445. doi: 10.1113/jphysiol.1979.sp012629. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Läuger P. Ion transport through pores: a rate-theory analysis. Biochim Biophys Acta. 1973 Jul 6;311(3):423–441. doi: 10.1016/0005-2736(73)90323-4. [DOI] [PubMed] [Google Scholar]
  15. Matsuda H., Saigusa A., Irisawa H. Ohmic conductance through the inwardly rectifying K channel and blocking by internal Mg2+. Nature. 1987 Jan 8;325(7000):156–159. doi: 10.1038/325156a0. [DOI] [PubMed] [Google Scholar]
  16. Methfessel C., Witzemann V., Takahashi T., Mishina M., Numa S., Sakmann B. Patch clamp measurements on Xenopus laevis oocytes: currents through endogenous channels and implanted acetylcholine receptor and sodium channels. Pflugers Arch. 1986 Dec;407(6):577–588. doi: 10.1007/BF00582635. [DOI] [PubMed] [Google Scholar]
  17. Taglietti V., Tanzi F., Romero R., Simoncini L. Maturation involves suppression of voltage-gated currents in the frog oocyte. J Cell Physiol. 1984 Dec;121(3):576–588. doi: 10.1002/jcp.1041210317. [DOI] [PubMed] [Google Scholar]
  18. Toselli M., Simoncini L., Taglietti V., Tanzi F. Acetylcholine-induced currents at plasma membrane of the frog oocyte. Neurosci Lett. 1985 Mar 15;54(2-3):179–184. doi: 10.1016/s0304-3940(85)80075-6. [DOI] [PubMed] [Google Scholar]
  19. Urban B. W., Hladky S. B. Ion transport in the simplest single file pore. Biochim Biophys Acta. 1979 Jul 5;554(2):410–429. doi: 10.1016/0005-2736(79)90381-x. [DOI] [PubMed] [Google Scholar]

Articles from The Journal of Physiology are provided here courtesy of The Physiological Society

RESOURCES