Occurrence of estrogen receptor alpha in bovine placentomes throughout mid and late gestation and at parturition.
The bovine placenta produces estrogens from the first trimester until the end of its life span. However, with the exception of the immediate prepartal and intrapartal phases, in which an involvement of placental estrogens has been suggested for the preparation of parturition, their function has not been elucidated yet. To test for a role of placental estrogens as local factors regulating placental growth and differentiation, placentomes from cows that were pregnant for 150, 220, 240, and 270 days, and parturient cows (3 animals per group) were screened immunohistochemically for the expression of estrogen receptor alpha (ERalpha). Indirect immunoperoxidase staining methods were applied using primary monoclonal antibodies (pmAbs) directed against the C-terminus (AER311, HT277) or the N-terminus (AER314, 1D5) of the ERalpha molecule. Both types of pmAbs identified ERalpha in stromal cells and capillary pericytes of the maternal caruncular septae. Using pmAb 1D5, the mean percentage of ERalpha-positive caruncular stromal cells decreased from 39.0% +/- 5.9% in pregnant cows to 17.5% +/- 8.3% at parturition (P = 0.011). Only pmAb recognizing the C-terminus identified ERalpha in the caruncular epithelium, in which positive reactions were found in all cells, with the exception of areas adjacent to the chorionic plate and to major chorionic villi, where the specific signal gradually faded and occasionally disappeared. No positive reactions were observed in the fetal part of the placentomes. The expression of ERalpha in bovine placentomes was further confirmed by the detection of ERalpha-specific mRNA by reverse transcriptase-polymerase chain reaction and by Western blot analysis. The results suggest a role for placental estrogens as paracrine factors involved in the regulation of placental growth and differentiation.
Schuler
Gerhard
G
Klinik für Geburtshilfe, Gynäkologie und Andrologie der Gross- und Kleintiere mit Tierärztlicher Ambulanz, Justus-Liebig-Universität, Frankfurter Strasse 106, D-35392 Giessen, Germany. gerhard.schuler@vetmed.uni-giessen.de
Wirth
Christina
C
Teichmann
Ursula
U
Failing
Klaus
K
Leiser
Rudolf
R
Thole
Hubert
H
Hoffmann
Bernd
B
D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002417:Cattle; D002824:Chorionic Villi / Q000737:chemistry; D047628:Estrogen Receptor alpha; D005260:Female; D005865:Gestational Age; D007124:Immunoenzyme Techniques; D007743:Labor, Obstetric; D010446:Peptide Fragments / Q000276:immunology; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D011960:Receptors, Estrogen / Q000032:analysis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000737:chemistry
D000911:Antibodies, Monoclonal; D047628:Estrogen Receptor alpha; D010446:Peptide Fragments; D012333:RNA, Messenger; D011960:Receptors, Estrogen