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Talk Abstract
The Sodium/Calcium Exchanger Affects the Plateau Fraction in Models for Electrical Bursting in Pancreatic beta-cells

Isabella Susa

Service de Chimie-Physique
Universite Libre de Bruxelles, CP 231
Boulevard du Triomphe
1050 Brussels, Belgium
e-mail isusa@ulb.ac.be

Joint work with David Gall.

The glucose-stimulated secretion of insulin from beta-cells in pancreatic islets is induced by bursting electrical activity, consisting of a periodic alternation of active and silent phases. The modulation of the plateau fraction (fraction of time spent in the active phase) is an essential factor in the regulation of insulin release (Meissner, H.P. and H. Schmelz, 1974).

The Na+/Ca2+ exchanger is a Ca2+-activated electrogenic Ca2+-transporter of the plasma membrane of the pancreatic beta-cells (Gall, D. et al., 1999). We have incorporated the Na+/Ca2+ exchange in different single-cell models (Sherman, A., 1996) to investigate its role on electrical bursting behavior and insulin secretion. We show that the depolarizing influence of the Na+/Ca2+ exchange current is able to prolong the burst duration and increase the plateau fraction. In addition, the Na+/Ca2+ exchange can provide a physiological mechanism, among others like K(ATP) channels, to increase the plateau fraction as the glucose concentration is raised.

Gall, D., J. Gromada, I. Susa, A. Herchuelz, P. Rorsman, and K. Bokvist. Significance of Na/Ca-exchange for Ca2+-buffering and electrical activity in mouse pancreatic beta-cells. {\it Biophysical. J.}, in press.

\noindent Meissner, H.P. and H. Schmelz. Membrane potential of beta-cells in pancreatic islets. {\it Pfl\"ugers Arch.}, 351:195-206, 1974.

Sherman, A. Contributions of modeling to understanding stimulus-secretion coupling in pancreatic beta-cells. {\it Am. J. of Phys.}, 271: E362-E372, 1996.

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1998-1999 Mathematics in Biology

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