Regulation of Ca(2+)-activated K+ currents by ciglitazone in rat pituitary GH3 cells

J Investig Med. 2000 Jul;48(4):259-69.


Background: Ciglitazone, an antidiabetic agent of the thiazolidinedione family, is known to be an activator of the peroxisome-proliferator activator receptor (PPAR)-gamma. The underlying mechanism of ciglitazone actions on ionic currents in neuroendocrine cells remains unclear.

Methods: The effects of ciglitazone on ionic currents were investigated in rat pituitary GH3 cells using the whole-cell and inside-out configurations of the patch-clamp technique.

Results: In GH3 cells, ciglitazone at 3-300 mumol/L caused a reversible increase in the amplitude of the Ca(2+)-activated K+ current (IK(Ca)) with a half-maximal concentration of 16 mumol/L. Under the inside-out patch recording mode, ciglitazone applied intracellularly increased the activity of the large-conductance Ca(2+)-activated K+ (BKCa) channels, but did not affect their single-channel conductance. However, troglitazone (30 mumol/L) caused a reduction in the channel activity. The ciglitazone-induced change in the kinetic behavior of BKCa channels is due to an increase in mean open time and a decrease in mean closed time, whereas the troglitazone-induced decrease in the channel activity is related to a decrease in mean open time and an increase in mean closed time. Ciglitazone caused a left shift in the midpoint for voltage-dependent opening. The ciglitazone-stimulated activity of BKCa channels is independent of internal Ca2+. Under the current clamp mode, ciglitazone (30 mumol/L) hyperpolarized the membrane potential.

Conclusions: This study shows that in addition to its activation of PPAR-gamma, ciglitazone can stimulate the activity of BKCa channels expressed in GH3 cells. These effects may affect membrane potentials and contribute to the ciglitazone-induced change in the functional activity of neurons or neuroendocrine cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Animals
  • Calcium / pharmacology*
  • Hypoglycemic Agents / pharmacology*
  • Membrane Potentials / drug effects
  • Pituitary Gland / drug effects
  • Potassium Channels / drug effects*
  • Rats
  • Thiazoles / pharmacology*
  • Thiazolidinediones*
  • Tumor Cells, Cultured


  • Hypoglycemic Agents
  • Potassium Channels
  • Thiazoles
  • Thiazolidinediones
  • Adenosine Triphosphate
  • Calcium
  • ciglitazone