Gabriel S. Khodr

The Effect of Luteinizing Hormone-Releasing Factor on Human Chorionic Gonadotropin Secretion

The effect of luteinizing hormone-releasing factor (LRF) on secretion of human chorionic gonadotropin (hCG) by the human placenta in culture was studied. A specific stimulation of hCG secretion was observed. The stimulation of hCG production correlated with the LRF dose in the culture medium. On the other hand, the secretion of human chorionic somatomammotropin was not affected. These data demonstrate a specific action of LRF on placental production of hCG in vitro.

Localization of Luteinizing Hormone-Releasing Factor in the Human Placenta

Luteinizing hormone-releasing factor (LRF) has been found to be produced by the placenta. In the present study, the localization of this releasing factor was delineated by the use of an immunofluorescnece technique. Intense fluorescence was localized in the cytotrophoblast, along the outer surface layer of the syncytiotrophoblast, and in the villous stroma. The cytoplasm of the syncytiotrophoblast did not exhibit any fluorescence. It may be speculated that placental LRF plays a role in regulating the production of human chorionic gonadotropin.

Extrahypothalamic Luteinizing Hormone-Releasing Factor (LRF): Release of Immunoreactive LRF in Vitro *

The human placenta in vitro releases luteinizing hormone-releasing factor (LRF) which is immunologically indistinguishable from hypothalamic LRF. The release of LRF by placental tissue increased during the 4 days of culture and exceeded the original tissue content more than 5-fold. These data suggest that the human placenta may synthesize an LRF molecule immunologically identical with hypothalamic LRF.

PRODUCTION AND ACTIVITY OF PLACENTAL RELEASING HORMONES

Publisher Summary This chapter discusses the production and activity of placental releasing hormones. The human placenta produces a number of steroid and protein hormones. Some of these have been chemically defined—for example, progesterone, human chorionic somatomammotropin (hCS), and human chorionic gonadotropin (hCG). There is also evidence for the presence of other pituitary hormone–like activities in the placenta, such as chorionic thyrotropin, adrenocorticotropic, and melanocyte-stimulating hormone. The factors involved in the control of these placental hormones are not known. However, a few agents have been shown to be effective in stimulating or inhibiting the release of these hormones. The human placenta contains a number of releasing and inhibiting hormones, such as gonadotropin-releasing hormone, thyrotropin-releasing hormone, somatotropin-releasing inhibiting factor. In addition to these hormones, human chorionic gonadotropin–releasing hormone (hCGnRH) has been detected in human placenta. The chapter also describes findings related to the chemical nature and activity of hCGnRH and its possible action during pregnancy. The hCGnRh is present primarily in the cytotrophoblast and its total content and concentration vary with gestational age.