Effect of excessive GnRH-binding substance on circulating maternal hCG in human pregnancy.

Gonadotropin-releasing hormone (GnRH) can stimulate the release of placental human chorionic gonadotropin (hCG). Thus, at the onset of these studies it was the objective to define the relationship of hCG to GnRH in the maternal circulation throughout pregnancy, focusing on early pregnancy. Blood samples were collected at 8, 10, 12, 14, 16, 28 and 36 weeks of gestation during labor and the GnRH and hCG levels were determined by radioimmunoassay. Of 39 pregnancies, a GnRH-binding substance was found in the maternal circulation of three. This GnRH-binding substance resulted in erroneous GnRH levels, due to the very high non-specific binding. In the pregnant women without this GnRH-binding substance, GnRH attained highest concentrations at 12-14 weeks. The typical peak of hCG at 8-10 weeks of gestation was observed in this group, while the group of patients having the GnRH-binding substance had significantly lower hCG levels. Each of the patients with circulating GnRH-binding substance had prior pregnancy(s) and two of the three had a prior pregnancy loss. The nature of this GnRH-binding substance was investigated using gel chromatography. After incubation of [125I]GnRH with patient plasma for 3 days this substance was shown to be of high molecular weight which was ethanol precipitable. This binding substance may therefore be an antibody, since it appears to be a high molecular weight protein requiring a number of days to bind the [125I] GnRH. This GnRH-binding substance may be of physiological importance, since the circulating hCG level was significantly less in the group of patients with this substance than in those without.

Gestational age-related inhibition of placental hCG, alpha hCG and steroid hormone release in vitro by a GnRH antagonist.

Human placental tissues have been shown to contain gonadotrophin-releasing hormone-(GnRH)-like activity. Thus, the effect of a potent GnRH antagonist (N-Ac-Pro1,D-p-Cl-Phe2,D-Nal(2)3,6-GnRH, obtained from Syntex Laboratories) on placental hormonal release was studied. Explant cultures of placentae of 6 to 15 weeks' gestation were studied. This GnRH antagonist did not inhibit the alpha human chorionic gonadotrophin (alpha hCG), human chorionic gonadotrophin (hCG), oestrone or oestradiol release from the six- and nine-week placental cultures, but greatly suppressed the release of these hormones in the placental cultures from 13- and 15-week gestations. Synthetic GnRH partially reversed the action of this antagonist on the hormonal releases in the 15-week placental cultures. These data demonstrate a gestational age-related action of this antagonist on placental hormonal release. Thus, a role for the endogenous GnRH-like activity of the placenta in the control of placental hormonogenesis is indicated.

Differential inhibition of human placental prostaglandin release in vitro by a GnRH antagonist.

Previously, we have demonstrated that the production of prostaglandins by human placental tissue varied with gestational age. In addition, we have shown that placental prostaglandin release was affected by GnRH, and that its response was also dependent on the gestational age of the placenta. Thus, we have studied the effect of a GnRH antagonist ([N-Ac-Pro1,D-p-Cl-Phe2,D-Nal(2)3,6-LHRH, Syntex Research, Palo Alto, CA) on basal prostaglandin release from placentas of 6 to 15 weeks' gestation and found that this antagonist (1 microgram/ml) effects an inhibition of the release of prostaglandin E, prostaglandin F, and 13,14-dihydro-15-keto-prostaglandin from placentas of 13 and 15 weeks of gestation. This effect was not overridden by GnRH at 10 times the antagonist concentration in the 13-week placental cultures, but was totally reversed by GnRH (10 micrograms/ml) in the 15-week placental cultures. These data demonstrate that this GnRH antagonist can affect human placental prostaglandin production at 13 to 15 weeks of gestation and indicate that endogenous placental GnRH-like activity may exert a control over placental prostaglandin release at this gestational stage.

Gonadotropin-releasing hormone effects on placental hormones during gestation: II. Progesterone, estrone, estradiol and estriol.

The release of progesterone (P), estrone (E1), estradiol (E2) and estriol (E3) from human placental tissue in vitro was found to be related to the gestational age of the placenta. The basal release of P, E1 and E2 on Day 1 of culture was highest from placentas of early gestation (9-13 wk). The release of P then declined, reaching a nadir by 15 wk, and continued at that level. The release of E1 and E2, reached a nadir at 17 weeks, and then again increased by term. In contrast, the basal release of E3 increased with increasing gestational age of the placenta. Thus, it appears that differing factors may influence placental P, E1, E2 and E3 production. In addition, the effect of synthetic gonadotropin-releasing hormone (GnRH) on these hormonal releases was studied. The stimulation of P by GnRH was greatest in placentas of 16 and 17 wk of gestation after extended culture when the basal release of P had declined. As much as a 240-fold increase was observed on the eighth day of culture. A large stimulation of P (32-fold) was also observed in the term placental cultures. A stimulation of E1 and E2 by GnRH was observed during the initial days of culture and in mid-gestational placental cultures (16-17 wk). A stimulation of E2 only was also observed at 13-15 wk and at term. A stimulation of E3 was observed in certain individual placentas. A correlation of the P and human chorionic gonadotropin (hCG) response to GnRH stimulation was noted, as well as an inverse relation of estrogens and hCG stimulation by GnRH. These data demonstrate that steroidogenic competence of the placenta differs with gestational age and that GnRH can influence steroid release. The degree and pattern of response to GnRH varied with the gestational age of the placenta and its endocrine milieu.

Gonadotropin-releasing hormone effects on placental hormones during gestation: I. Alpha-human chorionic gonadotropin, human chorionic gonadotropin and human chorionic somatomammotropin.

The release of alpha-human chorionic gonadotropin (alpha hCG), gonadotropin human chorionic gonadotropin (hCG) and human chorionic somatomammotropin (hCS) in vitro from placentas of different gestational ages was studied. In addition, the effect of gonadotropin-releasing hormone (GnRH) on these hormonal releases, as related to the gestational age of the placenta cultured and the dose of GnRH, was determined. The basal release of alpha hCG and hCG was greatest at 9-13 wk of gestation (1000-1500 ng/mg and 250-350 ng/mg, respectively). Lowest release rates were at term (28 ng/mg and 20 ng/mg, respectively). Hormonal release declined with extended culture, except from the cultures of 13- and 15-wk placentas, in which the initially high release continued throughout the 8 days of culture. The initial release of hCS was low at 6 wk, increased to maximum rates by 15 wk, and was similar to the initial rate of release at term. Gonadotropin-releasing hormone stimulated the release of alpha hCG and hCG most dramatically in cultures of 16-wk and 17-wk placentas, where as much as a 400- and 250-fold increase, respectively, on Day 6 of culture was observed (p less than 0.0001). In term placenta cultures after 6 days in vitro, a 20-fold stimulation of alpha hCG and a 10-fold increase of hCG was effected by GnRH (p less than 0.001). The largest responses of alpha hCG and hCG to GnRH were observed when estrogen levels were low. Dose-related responses were observed in some placentas, yet in some instances, maximal effects were attained with all doses utilized in these studies (0.2 to 50 micrograms/ml). These data demonstrate that human placentas of different gestational ages have varying hormonogenic capabilities in vitro. The data also establish that synthetic GnRH is capable of stimulating alpha hCG and hCG production, but the degree and pattern of response to GnRH stimulation are related to the gestational age of the placental tissue and its time in culture. The most responsive period to exogenous GnRH stimulation of alpha hCG and hCG release was on Days 5 and 6 of culture, when basal estrogen release was very low. These data support the hypothesis that hCG release might be controlled by a chorionic GnRH stimulation and suggest that local steroid levels may modulate the hCG response to GnRH stimulation.

Inhibition of hCG, alpha hCG and progesterone release from human placental tissue in vitro by a GnRH antagonist.

A dramatic suppression of hCG, alpha hCG and progesterone release from midgestation, human placentas in vitro was effected when incubated with 1 microgram/ml of an antagonist to GnRH. This inhibition of hormonal release occurred rapidly and was partially restored by the addition of GnRH. Human chorionic somatomammotropin was also suppressed, but only two days following the decline of the other hormones. These data demonstrate that an antagonist to GnRH can rapidly inhibit human placental hormone release.

Placental luteinizing hormone-releasing factor and its synthesis.

The synthesis of a placental luteinizing hormone-releasing factor (pLRF), which is immunologically, physiochemically, and biologically indistinguishable from synthetic LRF, was demonstrated. The incorporation of 3H-labeled leucine by human placental tissue in vitro into pLRF was determined by purification on carboxymethyl-cellulose and specific immunoprecipitation of the 3H-labeled pLRF. The specific activity of the pLRF released into the medium increased 100-fold from day 1 to day 2 of culture and attained a concentration of 2.84 microcuries per microgram. These data indicate that the pLRF that was released initially was endogenous, whereas that released subsequently reflected synthesis.

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.

Y-autosome translocation, gonadal dysgenesis, and gonadoblastoma.

A 5-year-old girl was discovered to have an abnormal karyotype with a translocation involving the Y chromosome. The primary complaint was slight physical growth retardation. Cytogenetic and endocrinologic evaluations were performed. The chromosomal complement exhibited a mosaicism: 45,X,t(Y;18)(q11;p11)/45,X0. The gonads of this patient were typical streaks containing no ova or follicles. A gonadoblastoma was present bilaterally.

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.

Content of luteinizing hormone-releasing factor in the human placenta.

Immunoreactive luteinizing hormone-releasing factor (LRF) was quantitated in the human placenta. It was found that the total placental content as well as the content per milligram of placental tissue varied with the stages of gestation. The fetal sex did not affect the LRF production. These studies establish that the placenta contains large amounts of LRF, immunologically identical to hypothalamic LRF.