Analysis of Ultrashort Feedback Regulation in Human Placenta: Synthesis and Secretion of GnRH by Human Trophoblastic Cells

Background: Gonadotropin-releasing hormone (GnRH) presumably controls placental growth and functions by autocrine/paracrine mechanisms, and is therefore an important part of the neuroendocrine network in human placenta. Aim: Our earlier work had indicated that GnRH was expressed in human placenta; in extension to these findings, we wanted to analyse synthesis and release of GnRH by trophoblastic cells. GnRH-associated peptide, colinearily synthesised with GnRH, was used as indicator of actual peptide synthesis. Method: First, we immunised rabbits with lipopeptides containing partial sequences of GnRH-associated peptide (GAP) and developed antibodies for immunohistochemical staining. Second, we set up a competitive enzyme immunoassay to measure GnRH: Non-biotinylated GnRH, GnRH analogues or trophoblastic cell culture supernatants were used to inhibit binding of biotinylated des-pGlu¹-GnRH to a monoclonal anti-GnRH antibody. Results: a) Placental sections stained positive for GAP in the layers of trophoblastic cells. b) GnRH could be detect by a competitive EIA in supernatants of placental cultures in concentrations between 200 and 5 nM. Conclusions: GnRH is synthesised and released by trophoblastic cells.

Key words

GnRH-Associated Peptide - GAP - Enzyme Immunoassay - Competitive - Fetal Bovine Serum