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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 586/6/1549    most recent jphysiol.2008.151274v1 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 Reeves, J. P. Articles by Condrescu, M. Search for Related Content PubMed PubMed Citation Articles by Reeves, J. P. Articles by Condrescu, M. Related Collections Cellular

¹ Department of Pharmacology & Physiology, University of Medicine and Dentistry of New Jersey, Graduate School of Biomedical Sciences, 185 South Orange Avenue, Newark, NJ 07101-1709, USA

This report describes the influence of fluid flow and osmotically induced volume changes on Na⁺–Ca²⁺ exchange (NCX) activity in transfected CHO cells. Exchange activity was measured as Na⁺-dependent Ca²⁺ or Ba²⁺ fluxes using the fluorescent probe fura-2. When exchange activity was initiated by superfusing Ba²⁺-containing solutions over the cells for a 20 s interval, a high rate of Ba²⁺ uptake was observed while the solution was being applied but the rate of Ba²⁺ uptake declined > 10-fold when the solution flow ceased. Ba²⁺ efflux in exchange for extracellular Na⁺ or Ca²⁺ (Ba²⁺–Ca²⁺ exchange) was similarly biphasic. During NCX-mediated Ca²⁺ uptake, a rapid increase in cytosolic [Ca²⁺] to a peak value occurred, followed by a decline in [Ca²⁺]_i to a lower steady-state value after solution flow ceased. When NCX activity was initiated by an alternate procedure that minimized the duration of solution flow, the rapid phase of Ba²⁺ influx was greatly reduced in magnitude and Ca²⁺ uptake became nearly monophasic. Solution superfusion did not produce any obvious changes in cell shape or volume. NCX-mediated Ba²⁺ and Ca²⁺ influx were also sensitive to osmotically induced changes in cell volume. NCX activity was stimulated in hypotonic media and inhibited in hypertonic media; the osmotically induced changes in activity occurred within seconds and were rapidly reversible. We conclude that NCX activity is modulated by both solution flow and osmotically induced volume changes.

(Received 17 January 2008; accepted after revision 25 January 2008; first published online 31 January 2008)
Corresponding author J. P. Reeves: Department of Pharmacology & Physiology, University of Medicine and Dentistry of New Jersey, Graduate School of Biomedical Sciences, 185 South Orange Avenue, Newark, NJ 07101-1709, USA. Email: reeves{at}umdnj.edu

This article has been cited by other articles:

				O. Chernysh, M. Condrescu, and J. P. Reeves Sodium-dependent inactivation of sodium/calcium exchange in transfected Chinese hamster ovary cells Am J Physiol Cell Physiol, October 1, 2008; 295(4): C872 - C882. [Abstract] [Full Text] [PDF]