A role for calcium in gonadotropin-releasing hormone (GnRH) stimulated secretion of chorionic gonadotrophin by first trimester human placental minces in vitro

Abstract

In vitro studies using first-trimester human placental minces have shown that stimulation of human chorionic gonadotrophin (hCG) secretion by gonadotrophin-releasing hormone (GnRH) is dependent upon the presence of extracellular calcium. Addition of GnRH to first-trimester placental minces in vitro was found to stimulate ⁴⁵Ca²⁺ uptake into placental minces, and the process was associated with an increase in immunoreactive hCG in the medium. Addition of GnRH to placental minces preloaded with ⁴⁵Ca²⁺ stimulated the efflux of ⁴⁵Ca²⁺ within one minute. The calmodulin inhibitors chlorpromazine and trifluoperazine inhibited the basal uptake and efflux of ⁴⁵Ca²⁺ suggesting the involvement of calmodulin in the mobilization of calcium in the placenta.