A phospholipase C inhibitor, U-73122, blocks TSH-induced inositol trisphosphate production, Ca2+ increase and arachidonic acid release in FRTL-5 thyroid cells

Xiao Dong Wang, Juliann G. Kiang, Robert C. Smallridge

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

To characterize the role of phospholipase C (PLC)-mediated intrathyroid signal transduction by thyrotropin, we studied the effect of U-73122, an aminosteroid inhibitor of PLC-dependent activity, on TSH-activated PLC-Ca2+ and arachidonic acid (AA) signalling systems in cultured FRTL-5 rat thyroid cells. In the presence of extracellular Ca2+, TSH (0.1 μM) increased intracellular free calcium concentration ([Ca2+]i) by 63 ± 6% with a sustained plateau phase, and AA release by 160 ± 16%. By deletion of extracellular Ca2+, TSH induced a similar maximal [Ca2+]i increase, but the plateau phase and AA release were entirely suppressed. U-73122 (5 μM) inhibited TSH stimulation of 3H-labelled inositol trisphosphates (IP3) production by 73 ± 3% (P < 0.01) in one study, and completely in another. U-73122 concentration-dependently blocked the TSH-induced Ca2+ increase in either the presence or absence of external Ca2+. U-73122 also showed a similar concentration-response inhibition of TSH-induced AA release. These results provide direct evidence of PLC mediation of TSH-stimulated signal transduction in FRTL-5 thyroid cells. TSH-induced external Ca2+ entry, as well as intracellular Ca2+ mobilization, is probably a PLC-mediated process. From an IP3-sensitive intracellular pool, TSH induces intracellular Ca2+ mobilization. External Ca2+ entry seems to be a prerequisite for TSH-induced AA release. U-73122 inhibition of both cytosolic Ca2+ increase and AA release further confirms [Ca2+]i dependence for TSH stimulation of AA release.

Original languageEnglish (US)
Pages (from-to)101-106
Number of pages6
JournalBBA - Molecular Cell Research
Volume1223
Issue number1
DOIs
StatePublished - Aug 11 1994

Keywords

  • (Rat)
  • (Thyroid cell)
  • Arachidonic acid
  • Calcium ion, intracellular
  • Inositol 1,4,5-trisphosphate
  • Phospholipase C
  • Thyrotropin

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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