HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dömötör, E. Articles by Adam-Vizi, V. Search for Related Content PubMed PubMed Citation Articles by Dömötör, E. Articles by Adam-Vizi, V.

Na⁺-Ca²⁺ exchange and its implications for calcium homeostasis in primary cultured rat brain microvascular endothelial cells

Eszter Dömötör, N. Joan Abbott * and Vera Adam-Vizi

The role of Na⁺-Ca²⁺ exchange in the regulation of the cytosolic free Ca²⁺ concentration ([Ca²⁺]_i) was studied in primary cultured rat brain capillary endothelial cells. [Ca²⁺]_i was measured by digital fluorescence imaging in cells loaded with fura-2.

ATP (100 µM) applied for a short period of time (6 s) caused a rise in [Ca²⁺]_i from 127 ± 3 (n = 290) to 797 ± 25 nM, which then declined to the resting level, with a t_½time required for [Ca²⁺]_i to decline to half of peak [Ca²⁺]_i) of 5·4 ± 0·09 s. This effect was independent of external Ca²⁺ and could be abolished by previously discharging the Ca²⁺ pool of the endoplasmic reticulum with thapsigargin (1 µM).

Application of thapsigargin (1 µM) or cyclopiazonic acid (10 µM) to inhibit the Ca²⁺-ATPase of the endoplasmic reticulum 6 s prior to ATP application did not influence the peak [Ca²⁺]_i but greatly reduced the rate of decline of [Ca²⁺]_i, with t_½ values of 15 ± 1·6 and 23 ± 3 s, respectively.

In the absence of external Na⁺ (Na⁺ replaced by Li⁺ or N-methylglucamine) the basal [Ca²⁺]_i was slightly elevated (152 ± 6 nM) and the restoration of [Ca²⁺]_i after the ATP stimulation was significantly slower (t_½, 7·3 ± 0·46 s in Li⁺ medium, 8·12 ± 0·4 s in N-methylglucamine medium).

The external Na⁺-dependent component of the [Ca²⁺]_i sequestration was also demonstrated in cells stimulated by ATP subsequent to addition of cyclopiazonic acid; in a Na⁺-free medium [Ca²⁺]_i remained at the peak level in 88 % of the cells after stimulation with ATP.

Addition of monensin (10 µM) in the presence of external Na⁺ increased the resting [Ca²⁺]_i to 222 ± 9 nM over ~1 min and subsequent removal of extracellular sodium resulted in a further increase in [Ca²⁺]_i to a peak of 328 ± 11 nM, which was entirely dependent on external Ca²⁺.

These findings indicate that a functional Na⁺-Ca²⁺ exchanger is present at the blood-brain barrier, which plays a significant role in shaping the stimulation-evoked [Ca²⁺]_i signal and is able to work in reverse mode under pharmacological conditions.

This article has been cited by other articles:

				M. Y. Kim, G. H. Seol, G. H. Liang, J. A. Kim, and S. H. Suh Na+-K+ pump activation inhibits endothelium-dependent relaxation by activating the forward mode of Na+/Ca2+ exchanger in mouse aorta Am J Physiol Heart Circ Physiol, November 1, 2005; 289(5): H2020 - H2029. [Abstract] [Full Text] [PDF]

				A. A. Gerencser and V. Adam-Vizi Mitochondrial Ca2+ Dynamics Reveals Limited Intramitochondrial Ca2+ Diffusion Biophys. J., January 1, 2005; 88(1): 698 - 714. [Abstract] [Full Text] [PDF]

				R. C. Brown, K. S. Mark, R. D. Egleton, and T. P. Davis Protection against hypoxia-induced blood-brain barrier disruption: changes in intracellular calcium Am J Physiol Cell Physiol, May 1, 2004; 286(5): C1045 - C1052. [Abstract] [Full Text] [PDF]

				L. Csanady and V. Adam-Vizi Ca2+- and Voltage-Dependent Gating of Ca2+- and ATP-Sensitive Cationic Channels in Brain Capillary Endothelium Biophys. J., July 1, 2003; 85(1): 313 - 327. [Abstract] [Full Text] [PDF]

				E. Domotor, O. Benzakour, J. H. Griffin, D. Yule, K. Fukudome, and B. V. Zlokovic Activated protein C alters cytosolic calcium flux in human brain endothelium via binding to endothelial protein C receptor and activation of protease activated receptor-1 Blood, June 15, 2003; 101(12): 4797 - 4801. [Abstract] [Full Text] [PDF]

				A. Savina, M. Furlan, M. Vidal, and M. I. Colombo Exosome Release Is Regulated by a Calcium-dependent Mechanism in K562 Cells J. Biol. Chem., May 23, 2003; 278(22): 20083 - 20090. [Abstract] [Full Text] [PDF]

				J.-C. Schneider, D. El Kebir, C. Chereau, J.-C. Mercier, J. Dall'Ava-Santucci, and A. T. Dinh-Xuan Involvement of Na+/Ca2+ exchanger in endothelial NO production and endothelium-dependent relaxation Am J Physiol Heart Circ Physiol, August 1, 2002; 283(2): H837 - H844. [Abstract] [Full Text] [PDF]

				B. Nilius and G. Droogmans Ion Channels and Their Functional Role in Vascular Endothelium Physiol Rev, October 1, 2001; 81(4): 1415 - 1459. [Abstract] [Full Text] [PDF]