Cytosolic free Ca2+ in human syncytiotrophoblast cells increased by gonadotropin-releasing hormone.
Effects of GnRH on free cytosolic Ca2+ concentrations ([Ca2+]i) were examined in individual first trimester human cytotrophoblast and syncytiotrophoblast cells by fura-2 microspectrofluorimetry. GnRH (10(-6) M) did not affect [Ca2+]i in cytotrophoblasts on days 2-9 of culture, with 50 cells tested each day. GnRH (10(-6) M) did not affect [Ca2+]i on days 2-3, but increased [Ca2+]i in 15% of culture-derived syncytiotrophoblasts on day 4 (8 of 52 cells) and in 48% on days 5-9 of culture (158 of 332 cells). Culture-derived syncytiotrophoblasts originated from four first trimester placentae. GnRH increased [Ca2+]i in a preliminary trial using syncytiotrophoblasts derived directly from a single first trimester placenta and cultured for 3 days (13 of 33 cells). Culture-derived first trimester syncytiotrophoblast cells that responded to 10(-6) M GnRH (28 of 63 cells) on day 6 also responded to GnRH at 10(-7) M (26 of 28 of the above cells), 10(-8) M (24 of 28 cells, 10(-9) M (22 of 28 cells), and 10(-10) M (3 of 28 cells). No cells responded to GnRH below a concentration of 10(-10) M. Desensitization of syncytiotrophoblasts by continuous GnRH perifusion (10(-6) M) and blockade of GnRH by competitive antagonism with Nal-Glu-GnRH (10(-6) M) suggested that effects of GnRH were receptor specific. The results provide direct evidence supporting the contention that the intracellular signaling resultant from GnRH receptor-ligand interactions in syncytiotrophoblasts may be at least partially mediated by transient increases in [Ca2+]i.
Currie
W D
WD
Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, Canada.
Setoyama
T
T
Lee
P S
PS
Baimbridge
K G
KG
Church
J
J
Yuen
B H
BH
Leung
P C
PC
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002452:Cell Count; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014327:Trophoblasts / Q000187:drug effects / Q000378:metabolism*
D005456:Fluorescent Dyes; C057805:LHRH, N-Ac-2-Nal(1)-4-Cl-Phe(2)-3-Pal(3)-Arg(5)-Glu(6)-AlaNH2(10)-; D007987:Gonadotropin-Releasing Hormone; D000001:Calcimycin; D002118:Calcium; D016257:Fura-2