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This Article Full Text Full Text (PDF) All Versions of this Article: 292/6/E1863    most recent 00047.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Yang, S.-K. Articles by Chen, C. Search for Related Content PubMed PubMed Citation Articles by Yang, S.-K. Articles by Chen, C.

Somatostatin decreases voltage-gated Ca²⁺ currents in GH3 cells through activation of somatostatin receptor 2

¹Prince Henry's Institute of Medical Research, Melbourne, Australia; ²Department of Physiology, Monash University, Melbourne, Australia; and ³UMR 549 INSERM, Faculté de Médecine Université Paris Descartes, Paris, France

Submitted 18 January 2007 ; accepted in final form 22 February 2007

The secretion of growth hormone (GH) is inhibited by hypothalamic somatostatin (SRIF) in somatotropes through five subtypes of the somatostatin receptor (SSTR1–SSTR5). We aimed to characterize the subtype(s) of SSTRs involved in the Ca²⁺ current reduction in GH3 somatotrope cells using specific SSTR subtype agonists. We used nystatin-perforated patch clamp to record voltage-gated Ca²⁺ currents, using a holding potential of –80 mV in the presence of K⁺ and Na⁺ channel blockers. We first established the presence of T-, L-, N-, and P/Q-type Ca²⁺ currents in GH3 cells using a variety of channel blockers (Ni⁺, nifedipine, -conotoxin GVIA, and -agatoxin IVA). SRIF (200 nM) reduced L- and N-type but not T- or P/Q-type currents in GH3 cells. A range of concentrations of each specific SSTR agonist was tested on Ca²⁺ currents to find the maximal effective concentration. Activation of SSTR2 with 10^–7 and 10^–8 M L-797,976 decreased the voltage-gated Ca²⁺ current and abolished any further decrease by SRIF. SSTR1, SSTR3, SSTR4, and SSTR5 agonists at 10^–7 M did not modify the voltage-gated Ca²⁺ current and did not affect the Ca²⁺ current response to SRIF. These results indicate that SSTR2 is involved mainly in regulating voltage-gated Ca²⁺ currents by SRIF, which contributes to the decrease in intracellular Ca²⁺ concentration and GH secretion by SRIF.

somatostatin receptor subtypes; somatostatin receptor agonist; somatotrope