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Distribution, expression and functional effects of small conductance Ca-activated potassium (SK) channels in rat

Karen Noble1, Rachel Floyd, Andre Shmygol

  • 1Department of Physiology, University of Liverpool, UK.

Cell Calcium
|December 9, 2009
PubMed

Insights

Small conductance (SK) channels, not previously studied in the myometrium, are expressed throughout pregnancy. Inhibition of SK channels significantly impacts uterine contractility and calcium signaling more than large conductance (BK) channels.

Area of Science:

  • Physiology
  • Pharmacology
  • Reproductive Biology

Background:

  • Calcium-activated potassium channels (KCa) are crucial for smooth muscle function.
  • Large conductance (BK) channels in the myometrium are well-studied, but small conductance (SK) channels remain largely uncharacterized.
  • SK channel dysregulation, specifically SK3, is linked to uterine dysfunction and parturition delays.

Purpose of the Study:

  • To characterize the expression of SK channel isoforms (SK1-3) in rat myometrium during pregnancy.
  • To investigate the functional role of SK channels in regulating myometrial cytosolic calcium ([Ca]) and contractility.
  • To compare the functional impact of SK channels with BK channels in the pregnant myometrium.

Main Methods:

  • Quantitative real-time PCR to assess SK channel transcript expression.
  • Immunohistochemistry to confirm SK channel protein localization.
  • Electrophysiology (patch-clamp) to measure ion currents and membrane potential.
  • In vitro myometrial contractility assays and calcium imaging.

Main Results:

  • Consistent expression of SK1, SK2, and SK3 channel transcripts and proteins was observed throughout pregnancy.
  • SK channel inhibition (using apamin and scyllatoxin) caused membrane depolarization and induced action potentials in quiescent myometrial cells.
  • Inhibition of SK channels significantly increased cytosolic [Ca] and enhanced force in spontaneously contracting myometrial strips.
  • The functional impact of SK channel inhibition on myometrial activity was greater than that of BK channel inhibition.

Conclusions:

  • SK1-3 channels are expressed and translated in the pregnant rat myometrium.
  • SK channels play a significant role in regulating membrane potential, outward currents, and calcium signaling during pregnancy.
  • SK channels contribute more to myometrial quiescence than BK channels, suggesting a critical role in maintaining uterine relaxation.

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