Stimulation of single L-type calcium channels in rat pituitary GH3 cells by thyrotropin-releasing hormone

Massimo Mantegazza, Cristina Fasolato, Jürgen Hescheler, Daniela Pietrobon

Research output: Contribution to journalArticle

Abstract

Hormonal stimulation of voltage-dependent Ca2+ channels in pituitary cells is thought to contribute to the sustained phase of Ca2+ entry and secretion induced by secretion stimulating hormones and has been suggested as a mechanism for refilling the Ca2+ stores. Using the cell-attached patch-clamp technique, we studied the stimulation of single Ca2+ channels by thyrotropin-releasing hormone (TRH) in rat GH3 cells. We show that TRH applied from the bath switched the activity of single L-type Ca2+ channels from a gating mode with very low open probability (p(o)) to a gating mode with slightly smaller conductance but 10 times higher p(o). Interconversions between these two gating modes were also observed under basal conditions, where the equilibrium was shifted towards the low p(o), mode. TRH applied from the pipette had no effect, indicating the involvement of a cytosolic compound in the stimulatory pathway. We show that TRH does not potentiate all the L-type Ca2+ channels in a given membrane patch and report evidence for co-expression of two functionally different L-type Ca2+ channels. Our results uncover the biophysical mechanism of hormonal stimulation of voltage-dependent Ca2+ channels in GH3 cells and are consistent with differential modulation of different subtypes of dihydropyridine-sensitive Ca2+ channels.

Original languageEnglish
Pages (from-to)1075-1083
Number of pages9
JournalEMBO Journal
Volume14
Issue number6
Publication statusPublished - Mar 15 1995

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Keywords

  • Ca channel
  • G protein
  • Gating mode
  • Patch-clamp
  • Signal transduction

ASJC Scopus subject areas

  • Genetics
  • Cell Biology

Cite this

Mantegazza, M., Fasolato, C., Hescheler, J., & Pietrobon, D. (1995). Stimulation of single L-type calcium channels in rat pituitary GH3 cells by thyrotropin-releasing hormone. EMBO Journal, 14(6), 1075-1083.