Responsiveness to gonadotropin releasing hormone of human term trophoblast cells in vitro: induction by estradiol.

Human trophoblast cells isolated from term placentae by enzymatic treatment and maintained in culture, spontaneously secrete hCG after 72hrs but fail to increase their gonadotropin secretion in response to exogenous GnRH. Treatment with estradiol for 24 hrs prior to challenge with GnRH induces the responsiveness to GnRH stimulation. This action of estradiol on trophoblast cells in independent of their stage of differentiation. The competitive displacement analysis of [125I] GnRH binding to estradiol-primed trophoblast cells indicated a single class of low affinity sites with Ka of 1.6 x 10(6) M-1, similar to that observed previously in placental membranes. To our knowledge this is the first demonstration of induction of GnRH receptors by estradiol in human trophoblast cells.