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|Title:||Identification of a Gonadotropin Releasing Hormone-Like Factor in the Rabbit Placenta (Pregnancy, Corpus Luteum, Fetus)|
|Author(s):||Nowak, Romana Angelika|
|Department / Program:||Animal Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Biology, Animal Physiology|
|Abstract:||First objective was to determine day at which maternal recognition of pregnancy occurs in the doe. We examined the effect of embryo removal on progesterone (P(,4)) and luteinizing hormone (LH) levels in pregnant does. We found that P(,4) and LH profiles of pregnant does that had embryos removed prior to day 7 were not different from those of pseudopregnant controls. Next we determined the effect of conceptus (fetus and fetal placenta) removal at days 11, 12 and 18 on maternal serum P(,4) and LH levels. Serum P(,4) and LH profiles of does whose conceptuses were removed on d 11 were identical to pseudopregnant controls. Conceptus removal on d 12 or 18 caused a precipitous decline in P(,4) levels within 48 h. These data demonstrate that maternal recognition of pregnancy occurs by d 12 of gestation.
We examined d 18 fetal placentas for biological and immunological gonadotropin releasing hormone (GnRH)-like activity. Immunological activity was determined using radioimmunoassay. GnRH levels (pg/mg protein) were 1.2-2.0 in placentas and <0.2 for liver. Biological activity was determined by adding placental extracts to dispersed rabbit pituitary cells and checking for increased LH release. Placental extracts increased LH release significantly while liver had no effect. The immunological GnRH-like factor eluted in the same fractions as a GnRH standard following molecular sieve chromatography. A GnRH antagonist was able to partially suppress ((TURN)40%) the biological activity of placental extracts.
Placental tissue was placed in a perifusion system and challenged with 60mM K('+) to determine whether GnRH is secreted. Placentas had 3-4 fold higher GnRH output than liver or spleen and responded with a 78% increase in GnRH release following K('+). GnRH concentrations measured in uterine vein of pregnant does were not different from peripheral blood. GnRH was measured in maternal and fetal placentas at d 12, 18 and 28 of gestation. Concentrations in fetal placentas were highest at d 18 and lowest at d 28. GnRH was present in maternal components. These results indicate that an immunological and biological GnRH-like factor is present in the rabbit placenta after d 12 of gestation. GnRH is secreted by the placenta but not systemically into the uterine vein.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-15|