IMPLANTATION AND PREGNANCY - A
Monday, August 2, 2004
10:30 AM–12:30 PM
(242) THE INOSITOL PHOSPHATES cAMP, cGMP, AND ARACHIDONIC ACID METABOLIC PATHWAYS ARE NOT INVOLVED IN THE HORMONAL SECRETORY RESPONSE TO ALBUMIN FROM HUMAN TERM PLACENTA.
Lambot, Nathalie1, Lebrun, Philippe2, Delporte, Christine3, Sener, Abdullah1, Graff, Guy1, Delogne-Desnoeck, Josiane1, Vanbellinghen, Anne Marie1, Meuris, Sylvain1, 1 Université Libre de Bruxelles, Brussels, Belgium2 Université Libre de Bruxelles, Brussels, Belgium3 Université Libre de Bruxelles, Brussels, Belgium
ABSTRACT- Albumin, as well as other colloidal agents such as polygelin or dextran, is reported to stimulate the release of placental lactogen (hPL) and chorionic gonadotropin (hCG) from human term placental explants. This triggering effect is independent of extracellular Ca2+ but is accompanied by a 45Ca2+ outflow from preloaded placental explants. The present study was conducted to further investigate events linking extracellular albumin to the hCG and hPL secretion. Albumin (5%, w/v) did not modify the inositol phosphates (IPs), cAMP and cGMP contents in the placental explants. Addition of NaF (20 mM + AlCl3 10 M), forskolin (25 M) and sodium nitroprusside (500 M), known activators of the IPs, cAMP, cGMP pathways, significantly increased the respective second messengers villous contents. None of these agents modulated the hPL and hCG releases from syncytiotrophoblast. Albumin (5%)provoked a marked increase in 3H arachidonic acid (AA) outflow from preloaded and perifused explants. Nevertheless, benzoyl-ATP (100 M)and mastoparan (10 M), known activators of the phospholipase A2 pathway, failed to modify the 3H AA outflow. Albumin (5%) could also stimulate the 3H oleic acid outflow, a fatty acid not released at the phospholipase A2 step. Dextran (4.5%), another colloidal agent, failed to elicit these fatty acid outflows.These data suggest that the triggering effect of albumin on the hormonal release from placenta does not involve the IPs, cAMP, cGMP, and AA metabolic pathways. The albumin stimulation of fatty acids outflow from placental explants emphasizes a specific interaction between albumin and the syncytiotrophoblast.
KEY WORDS: hCG, cellular messengers, albumin, hPL