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Thyrotropin-releasing hormone activates KCa channels in gastric smooth muscle cells via intracellular Ca2+ release

P S Petkova-Kirova1, L T Lubomirov, H S Gagov

  • 1Institute of Biophysics, Bulgarian Academy of Sciences, Sofia.

General Physiology and Biophysics
|August 18, 2001
PubMed

Insights

Thyrotropin-releasing hormone (TRH) inhibits gastric smooth muscle contractions by activating potassium channels. This research reveals TRH

Area of Science:

  • Gastroenterology
  • Neuroendocrinology
  • Smooth Muscle Physiology

Background:

  • Thyrotropin-releasing hormone (TRH) is present in gastric juice.
  • Its direct effects on gastric smooth muscle remain uninvestigated.

Purpose of the Study:

  • To investigate the direct effects of TRH on gastric smooth muscle.
  • To elucidate the cellular mechanisms underlying TRH's action on gastric smooth muscle.

Main Methods:

  • Contraction studies on gastric strips.
  • Patch clamp electrophysiology on single smooth muscle cells.
  • Pharmacological manipulation using channel inhibitors and signaling pathway modulators.

Main Results:

  • TRH inhibited acetylcholine- and BaCl2-induced gastric contractions.
  • TRH inhibited voltage-dependent Ca2+ currents and activated whole-cell K+ currents in single cells.
  • TRH's effects on K+ currents and membrane potential were dependent on intracellular Ca2+ release and phospholipase C activity, but not protein kinase C.

Conclusions:

  • TRH activates K+ channels through inositol-1,4,5-trisphosphate-mediated Ca2+ release, leading to hyperpolarization and relaxation.
  • TRH may function physiologically as a local regulator of gastric smooth muscle tone.

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