Expression of growth hormone and its receptor in the placental and feto-maternal environment during early pregnancy in sheep

In a previous study we showed the existence of GH in the ovine placenta. We now supplement the information available on placental GH and describe the presence and distribution of GH receptor (GH-R) messenger RNA (mRNA) in ute rine, fetal, and placental tissues during early pregnancy. GH mRNA. was not detected in the placenta before day 27 (d27). Its expression peaked betwee n d40 and d45 and fell after d55. GH mRNA was localized in the trophectoder m and syncytium. During the d35-d50 period, concentrations of GH in the mat ernal circulation were not increased. In umbilical blood, however, GH was d etected from d35 and was presumed to be of placental origin, because GH mRN A was not detected in the fetal pituitary gland on d40. We report on GH-R m RNA expression in the placenta between d20-d120. The relative abundance of GH-R transcripts increased significantly between d25-d43. In the endometriu m, GH-R mRNA was detected from d8-d120 of pregnancy and from d4-d16 of the cycle. GH-R mRNA was localized in the trophectoderm, fetal mesoderm, and ma ternal uterine stroma. In the fetal liver, GH-R mRNA was first detectable o n d35. The results of this study indicate that between d35-d50 of pregnancy , the endometrium, placenta, and fetus are all potential targets for the pl acental GH.