Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents

This Article Full Text Full Text (PDF, 171K) PPT slides of all figures Alert me when this article is cited Citation Map Services Email this article Similar articles in this journal Similar articles in PubMed Alert me to new content in the JGP Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Wacke, M. Articles by Thiel, G. Search for Related Content PubMed PubMed Citation Articles by Wacke, M. Articles by Thiel, G. Social Bookmarking                            What's this?

Original Article

^a Albrecht-von-Haller Institute for Plant Sciences, Plant Biophysics, University of Göttingen, 37073 Göttingen, Germany
Department of Botany, TU-Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany.49-6151-164630

thiel{at}bio.tu-darmstadt.de

Electrically triggered action potentials in the giant alga Chara corallina are associated with a transient rise in the concentration of free Ca²+ in the cytoplasm (Ca²+_cyt). The present measurements of Ca²+_cyt during membrane excitation show that stimulating pulses of low magnitude (subthreshold pulse) had no perceivable effect on Ca²+_cyt. When the strength of a pulse exceeded a narrow threshold (suprathreshold pulse) it evoked the full extent of the Ca²+_cyt elevation. This suggests an all-or-none mechanism for Ca²+ mobilization. A transient calcium rise could also be induced by one subthreshold pulse if it was after another subthreshold pulse of the same kind after a suitable interval, i.e., not closer than a few 100 ms and not longer than a few seconds. This dependency of Ca²+ mobilization on single and double pulses can be simulated by a model in which a second messenger is produced in a voltage-dependent manner. This second messenger liberates Ca²+ from internal stores in an all-or-none manner once a critical concentration (threshold) of the second messenger is exceeded in the cytoplasm. The positive effect of a single suprathreshold pulse and two optimally spaced subthreshold pulses on Ca²+ mobilization can be explained on the basis of relative velocity for second messenger production and decomposition as well as the availability of the precursor for the second messenger production. Assuming that inositol-1,4,5,-trisphosphate (IP₃) is the second messenger in question, the present data provide the major rate constants for IP₃ metabolism.

Key Words: calcium mobilization • Fura-2 • simulation • voltage-dependent second messenger production

CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				W.-H. Zhang, N. A. Walker, J. W. Patrick, and S. D. Tyerman Pulsing Cl- channels in coat cells of developing bean seeds linked to hypo-osmotic turgor regulation J. Exp. Bot., May 1, 2004; 55(399): 993 - 1001. [Abstract] [Full Text] [PDF]

				J. Martinez-Pinna, G. Tolhurst, I. S. Gurung, J. I. Vandenberg, and M. P. Mahaut-Smith Sensitivity limits for voltage control of P2Y receptor-evoked Ca2+ mobilization in the rat megakaryocyte J. Physiol., February 15, 2004; 555(1): 61 - 70. [Abstract] [Full Text] [PDF]

				M. Tazawa and M. Kikuyama Is Ca2+ Release from Internal Stores Involved in Membrane Excitation in Characean Cells? Plant Cell Physiol., May 15, 2003; 44(5): 518 - 526. [Abstract] [Full Text] [PDF]

				E. Krol, H. Dziubinska, and K. Trebacz Low-Temperature Induced Transmembrane Potential Changes in the Liverwort Conocephalum conicum Plant Cell Physiol., May 15, 2003; 44(5): 527 - 533. [Abstract] [Full Text] [PDF]

				D. Thomas, M. J Mason, and M. P Mahaut-Smith Depolarisation-evoked Ca2+ waves in the non-excitable rat megakaryocyte J. Physiol., December 1, 2001; 537(2): 371 - 378. [Abstract] [Full Text] [PDF]

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents