| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Biophysical Journal 72: 175-187 (1997)
© 1997 the Biophysical Society
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada.
ABSTRACT
Free Ca2+ near Ca2+ channel pores is expected to be lower in cardiomyocytes dialyzed with bis-(o-amino-phenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) than with ethyleneglycol-bis-(beta-aminoethyl)-N,N,N',N'-tetraacetic acid (EGTA) because BAPTA chelates incoming Ca2+ more rapidly. The consequences of intracellular Ca2+ buffering by BAPTA (0.2-60 mM) and by EGTA (0.2-67 mM) on whole-cell L-type Ca2+ current (ICa,L) were investigated in voltage-clamped guinea pig ventricular cardiomyocytes; bulk cytoplasmic free Ca2+ (Cac2+) was monitored using the fluorescent Ca2+ indicator indo-1. ICa,L was augmented by approximately 12-fold when BAPTA in the cell dialysate was increased from 0.2 to 50 mM (half-maximal stimulation at 31 mM), whereas elevating internal EGTA from 0.2 to 67 mM increased ICa,L only by approximately 2-fold. Cac2+ was < 20 nM with internal BAPTA or EGTA > or = 20 mM. While EGTA up to 67 mM had only an insignificant inhibitory effect on the stimulation of ICa,L by 3 microM forskolin, ICa,L in 50 mM BAPTA-dialyzed myocytes was insensitive to forskolin-induced elevation of adenosine 3',5'-cyclic monophosphate (cAMP); conversely, ICa,L in cAMP-loaded cells was unresponsive to BAPTA dialysis. Cell dialysis with BAPTA, but not with EGTA, accelerated the slow component of ICa,L inactivation (tau S) without affecting its fast component (tau F), resembling the effects of cAMP-dependent phosphorylation. BAPTA-stimulated ICa,L was inhibited by acetylcholine and by the cAMP-dependent protein kinase (PKA) blocker H-89. These results suggest that BAPTA-induced lowering of peri-channel Ca2+ stimulates cAMP synthesis and channel phosphorylation by disinhibiting Ca(2+)-sensitive adenylyl cyclase.
This article has been cited by other articles:
 |
|
 |
|
  M. Rousset, T. Cens, A. Gouin-Charnet, F. Scamps, and P. Charnet Ca2+ and Phosphatidylinositol 4,5-Bisphosphate Stabilize a G{beta}{gamma}-sensitive State of CaV2 Ca2+ Channels J. Biol. Chem., April 9, 2004; 279(15): 14619 - 14630. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. H. duBell and T. B. Rogers Protein phosphatase 1 and an opposing protein kinase regulate steady-state L-type Ca2+ current in mouse cardiac myocytes J. Physiol., April 1, 2004; 556(1): 79 - 93. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. G.A. Volders, M. Stengl, J. M. van Opstal, U. Gerlach, R. L.H.M.G. Spatjens, J. D.M. Beekman, K. R. Sipido, and M. A. Vos Probing the Contribution of IKs to Canine Ventricular Repolarization: Key Role for {beta}-Adrenergic Receptor Stimulation Circulation, June 3, 2003; 107(21): 2753 - 2760. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Dun, T. Yagi, M. R Rosen, and P. A Boyden Calcium and potassium currents in cells from adult and aged canine right atria Cardiovasc Res, June 1, 2003; 58(3): 526 - 534. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Kurata, I. Hisatome, S. Imanishi, and T. Shibamoto Dynamical description of sinoatrial node pacemaking: improved mathematical model for primary pacemaker cell Am J Physiol Heart Circ Physiol, November 1, 2002; 283(5): H2074 - H2101. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Pelzer, C. La, and D. J. Pelzer Phosphorylation-dependent modulation of cardiac calcium current by intracellular free magnesium Am J Physiol Heart Circ Physiol, October 1, 2001; 281(4): H1532 - H1544. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.-B. Shen and A. J. Pappano Carbachol Inhibits the L-Type Ca2+ Current Augmented by 1,2-bis(2-Aminophenoxy)ethane-N,N,N',N'-Tetraacetic Acid in Guinea Pig Ventricular Myocytes: Calcium-Sensitivity Hypothesis for Muscarinic Inhibition J. Pharmacol. Exp. Ther., August 1, 2001; 298(2): 857 - 864. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. A. Aiello and H. E. Cingolani Angiotensin II stimulates cardiac L-type Ca2+ current by a Ca2+- and protein kinase C-dependent mechanism Am J Physiol Heart Circ Physiol, April 1, 2001; 280(4): H1528 - H1536. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Zaniboni, A. E. Pollard, L. Yang, and K. W. Spitzer Beat-to-beat repolarization variability in ventricular myocytes and its suppression by electrical coupling Am J Physiol Heart Circ Physiol, March 1, 2000; 278(3): H677 - H687. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Carmeliet Cardiac Ionic Currents and Acute Ischemia: From Channels to Arrhythmias Physiol Rev, July 1, 1999; 79(3): 917 - 1017. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Wu, L. B. MacMillan, R. B. McNeill, R. J. Colbran, and M. E. Anderson CaM kinase augments cardiac L-type Ca2+ current: a cellular mechanism for long Q-T arrhythmias Am J Physiol Heart Circ Physiol, June 1, 1999; 276(6): H2168 - H2178. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Schroder and S. Herzig Effects of beta 2-adrenergic stimulation on single-channel gating of rat cardiac L-type Ca2+ channels Am J Physiol Heart Circ Physiol, March 1, 1999; 276(3): H834 - H843. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Yamaoka, T. Yuki, K. Kawase, M. Munemori, and I. Seyama Temperature-sensitive intracellular Mg2+ block of L-type Ca2+ channels in cardiac myocytes Am J Physiol Heart Circ Physiol, March 1, 2002; 282(3): H1092 - H1101. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
