Regulation of GnRH I receptor gene expression by the GnRH agonist triptorelin, estradiol, and progesterone in the gonadotroph-derived cell line alphaT3-1.
The secretion of luteinizing hormone (LH) and the GnRH receptor (GnRH-R) concentration are modulated by ovarian steroids and GnRH. To elucidate whether this regulation is due to alterations at the transcriptional level, we examined the GnRH I-R mRNA expression in the gonadotroph-derived cell line alphaT3-1 treated with different estradiol and progesterone paradigms and the GnRH I agonist triptorelin. alphaT3-1 cells were treated with different steroid paradigms: 1 nM estradiol or 100 nM progesterone for 48 h alone or in combination. Cells were exposed to 10 nM or 100 pM triptorelin for 30 min, 3 h, 9 h, or, in pulsatile way, with a 5-min pulse per hour. The GnRH I-R mRNA was determined by Northern blot analysis. GnRH I-R mRNA from cells treated with continuous triptorelin decreased in a time- and concentration-dependent manner. Pulsatile triptorelin increased GnRH I-R gene expression. Progesterone alone further enhanced this effect, whereas estradiol and its combination with progesterone diminished it. Continuous combined treatment with estradiol and progesterone lead to a significant decrease of GnRH I-R mRNA by 30% and by 35% for estradiol alone. The addition of 10 nM triptorelin for 30 min or 3 h could not influence that steroid effect. In conclusion, estradiol and progesterone exclusively decreased GnRH I-R mRNA in alphaT3-1 cells no matter whether they are treated additionally with the GnRH I agonist triptorelin. The enhanced sensitivity of gonadotrophs and GnRH I-R upregulation by estradiol is not due to increased GnRH I gene expression because GnRH I-R mRNA is downregulated by estradiol and progesterone. Other pathways of the GnRH I-R signal transduction might be involved.
Weiss
J M
JM
Department of Obstetrics and Gynaecology, Medical University Luebeck, 23538 Luebeck, Germany. jmweiss1@hotmail.com
Polack
S
S
Treeck
O
O
Diedrich
K
K
Ortmann
O
O
D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D052681:Gonadotrophs / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology; D008186:Luteolytic Agents / Q000494:pharmacology*; D051379:Mice; D011374:Progesterone / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011966:Receptors, LHRH / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D017329:Triptorelin Pamoate / Q000494:pharmacology*
C484844:GNRHR protein, human; D008186:Luteolytic Agents; D012333:RNA, Messenger; D011966:Receptors, LHRH; D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol