Quantitative Gonadotropin-Releasing Hormone: DISCUSSION(3)
The role of GnRH in controlling placental hCG production and secretion has been fully demonstrated both in vitro and in vivo, especially in first-trimester placenta. The stimulatory effect appears to be receptor-dependent, since GnRH antagonist (GnRH-ant) blocks both the GnRH- and GnRH-a-induced effects. Furthermore, GnRH-ant reduces the amplitude of spontaneous placental hCG pulses, suggesting a direct blockage of endogenous placental GnRH. Recently, an antibody against GnRH has been described in the maternal circulation of pregnant women with previous miscarriages and low levels of hCG, reinforcing the important role of GnRH in human implantation and placentation.
In previous studies, GnRH receptor mRNA was reported to be present in 23% of the nonmalignant endometrial samples studied and in 77% of endometrial cancers. In our study, we detected the mRNA of GnRH receptor in 30% of the endometrial samples by performing one round of PCR; however, by nested PCR we were able to detect the receptor in all the endometrial tissue specimens studied both in the follicular and in the luteal phase. This indicates that although the GnRH receptor is expressed at low levels, it is present in the human endometrium of fertile women throughout the entire menstrual cycle. buy ventolin inhalers
Seshagiri et al. showed that immunoreactive GnRH and CG were produced in vitro by cultured rhesus monkey embryos during the entire peri-attachment period, from morula to attached blastocyst stage, and that the GnRH secretion commenced before that of hCG. Moreover, embryos that failed to hatch and attach secreted lower amounts of GnRH into the medium in contrast to those that did reach later stages of development; at the same time, CG was very low or absent in the medium of these embryos.