Effect of IPs, cAMP, and cGMP on the hPL and hCG secretion from human term placenta

The acute control of human placental lactogen (hPL) and chorionic gonadotrophin (hCG) secretion by the placenta remains elusive. The in vitro release of both hormones can be stimulated by calcium inflow and by albumin. To investigate the placental secretory response to putative ligand(s) present in the maternal circulation, we evaluated the coupling of the hPL and hCG releases from term placenta with intracellular signaling pathways. Addition of NaF, forskolin or sodium nitroprusside, activators of the inositol phosphates (IPs), cAMP and cGMP pathways, significantly increased their respective messengers in villous explants but failed to affect the hPL and hCG releases from syncytiotrophoblast. By contrast, albumin did not modify the IPs, cAMP and cGMP villous content but significantly stimulated the placental hormonal release. These data suggest that the hPL and hCG secretion is not regulated through the IPs, cAMP and cGMP signaling pathways.