Molecular Human Reproduction, Vol. 7, No. 1, 3-9,
January 2001
© 2001 European Society of Human Reproduction and Embryology
Reproductive endocrinology |
Comparison of the effects of GnRH-I and GnRH-II on HCG synthesis and secretion by first trimester trophoblast
Department of Obstetrics and Gynaecology, Clinic of Infertility and Gynaecological Endocrinology, WHO Collaborating Centre in Human Reproduction, University Hospital of Geneva, 32 Boulevard de la Cluse, 1211 Geneva, Switzerland
Abstract
Gonadotrophin-releasing hormone (GnRH) is an important factor in the regulation of the synthesis and secretion of gonadotrophins from the pituitary gland. An isoform of this decapeptide, GnRH-II, with an amino acid sequence 70% homologous to GnRH-I, has been recently described. Since the physiological effects of GnRH-II are not yet known, we undertook the present study to see whether GnRH-II could be involved in the secretion and synthesis of HCG in first trimester trophoblast. We incubated cytotrophoblastic cells (CTB) with GnRH-I or GnRH-II, for 4 or 96 h and collected the media at different times thereafter. We also performed experiments with placental tissue, where GnRH-I or GnRH-II was added to perifused placental explants, and samples were collected every 3 min. Total amounts of human chorionic gonadotrophin (HCG) were measured in all samples by enzyme-linked immunosorbent assay. GnRH-I was more potent than GnRH-II when incubated for 4 h with CTB, as indicated by increased HCG secretion at 8 h and at 24 h. GnRH-I, but not GnRH-II, down-regulated HCG secretion when incubated for 96 h. GnRH-I significantly increased HCG secretion by the explants, while GnRH-II had a lesser effect. Both induced a pulse of HCG immediately after their injection. Our data show that GnRH-I has more effect than GnRH-II on HCG synthesis and secretion. This difference could be explained by different pathways of GnRH degradation, different receptor affinities, or even by different types of placental GnRH receptor.
GnRH-I/GnRH-II/HCG/placenta/trophoblast
Notes
1 To whom correspondence should be addressed at: Clinique de Stérilité et d'Endocrinologie Gynécologique, Hôpital Cantonal Universitaire de Genève, 32 Boulevard de la Cluse, 1211 Genève 14, Switzerland. E-mail: dorina.islami{at}hcuge.ch
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