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This Article Full Text Full Text (PDF) All Versions of this Article: 572/3/691    most recent jphysiol.2005.102368v1 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 Vignali, S. Articles by Welling, A. Search for Related Content PubMed PubMed Citation Articles by Vignali, S. Articles by Welling, A. Related Collections Cellular

¹ Institut für Pharmakologie und Toxikologie
² Institut für Molekulare Medizin, TU München, Biedersteiner Strasse 29, D-80802 München, Germany

Insulin and glucagon are the major hormones of the islets of Langerhans that are stored and released from the B- and A-cells, respectively. Both hormones are secreted when the intracellular cytosolic Ca²⁺ concentration ([Ca²⁺]_i) increases. The [Ca²⁺]_i is modulated by mutual inhibition and activation of different voltage-gated ion channels. The precise interplay of these ion channels in either glucagon or insulin release is unknown, owing in part to the difficulties in distinguishing A- from B-cells in electrophysiological experiments. We have established a single-cell RT-PCR method to identify A- and B-cells from the mouse. A combination of PCR, RT-PCR, electrophysiology and pharmacology enabled us to characterize the different sodium and calcium channels in mouse islet cells. In both A- and B-cells, 60% of the inward calcium current (I_Ca) is carried by L-type calcium channels. In B-cells, the predominant calcium channel is Ca_V1.2, whereas Ca_V1.2 and Ca_V1.3 were identified in A-cells. These results were confirmed by using mice carrying A- or B-cell-specific inactivation of the Ca_V1.2 gene. In B-cells, the remaining I_Ca flows in equal amounts through Ca_V2.1, Ca_V2.2 and Ca_V2.3. In A-cells, 30 and 15% of I_Ca is due to Ca_V2.3 and Ca_V2.1 activity, respectively, whereas Ca_V2.2 current was not found in these cells. Low-voltage-activated T-type calcium channels could not be identified in A- and B-cells. Instead, two TTX-sensitive sodium currents were found: an early inactivating and a residual current. The residual current was only recovered in a subpopulation of B-cells. A putative genetic background for these currents is Na_V1.7.

(Received 24 November 2005; accepted after revision 28 February 2006; first published online 2 March 2006)
Corresponding author A. Welling: Institut für Pharmakologie und Toxikologie, TU München, Biedersteiner Strasse 29, D-80802 München, Germany. Email: welling{at}ipt.med.tu-muenchen.de

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