TY - JOUR
T1 - A phospholipase C inhibitor, U-73122, blocks TSH-induced inositol trisphosphate production, Ca2+ increase and arachidonic acid release in FRTL-5 thyroid cells
AU - Wang, Xiao Dong
AU - Kiang, Juliann G.
AU - Smallridge, Robert C.
PY - 1994/8/11
Y1 - 1994/8/11
N2 - 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.
AB - 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.
KW - (Rat)
KW - (Thyroid cell)
KW - Arachidonic acid
KW - Calcium ion, intracellular
KW - Inositol 1,4,5-trisphosphate
KW - Phospholipase C
KW - Thyrotropin
UR - http://www.scopus.com/inward/record.url?scp=0028168278&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028168278&partnerID=8YFLogxK
U2 - 10.1016/0167-4889(94)90078-7
DO - 10.1016/0167-4889(94)90078-7
M3 - Article
C2 - 8061042
AN - SCOPUS:0028168278
SN - 0167-4889
VL - 1223
SP - 101
EP - 106
JO - BBA - Molecular Cell Research
JF - BBA - Molecular Cell Research
IS - 1
ER -