Rapid nongenomic effects of 3,5,3'-triiodo-L-thyronine on the intracellular pH of L-6 myoblasts are mediated by intracellular calcium mobilization and kinase pathways

Endocrinology. 2004 Dec;145(12):5694-703. doi: 10.1210/en.2004-0890. Epub 2004 Sep 2.


L-T3 and L-T4 activated the Na+/H+ exchanger of L-6 myoblasts, with a fast nongenomic mechanism, both in the steady state and when cells undergo acid loading with ammonium chloride. Monitored with the intracellular pH-sensitive fluorescent probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, activation of the exchanger appeared to be initiated at the plasma membrane, because T3-agarose reproduced the effect of L-T3, and triiodothyroacetic acid, a hormone analog previously shown to inhibit membrane actions of thyroid hormone, blocked the action of L-T3 on the exchanger. We show here for the first time that transduction of the hormone signal in this nongenomic response requires tyrosine kinase-dependent phospholipase C activation and two different signaling pathways: 1) mobilization of intracellular calcium, assessed by the fluorescent probe fura-2, through activation of inositol trisphosphate receptors and without contributions from extracellular calcium or ryanodine receptors; and 2) protein phosphorylation involving protein kinase C and MAPK (ERK1/2), as shown by the use of kinase inhibitors and by immunoblotting for activated kinases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amiloride / analogs & derivatives*
  • Amiloride / pharmacology
  • Animals
  • Anti-Arrhythmia Agents / pharmacology
  • Calcium / metabolism*
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • Hydrogen-Ion Concentration / drug effects*
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / physiology*
  • Muscle, Skeletal / cytology
  • Myoblasts / drug effects
  • Myoblasts / enzymology*
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • Rats
  • Sodium-Hydrogen Exchangers / metabolism
  • Triiodothyronine / pharmacology*


  • Anti-Arrhythmia Agents
  • Enzyme Inhibitors
  • Sodium-Hydrogen Exchangers
  • Triiodothyronine
  • Amiloride
  • Protein Kinase C
  • Calcium
  • ethylisopropylamiloride