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Archives of gynecology

, Volume 229, Issue 4, pp 259–264 | Cite as

Regulation of ovarian LH/HCG receptors in pregnant rats

  • U. Müller
  • Th. Bauknecht
  • J. W. Siebers
Article

Summary

On the 16th day of pregnancy rat ovaries contain a high concentration of LH/HCG receptors. After the injection of 200 IU HCG the ovarian membranes lose almost completely their capacity to bind125I-HCG. Measurement of occupied receptors shows that the initial loss is associated with occupancy of the LH/HCG receptors, but that the prolonged reduction of binding capacity is not attributable to receptor occupancy. The bound hormone is largely cleaved from the ovary within 4 days. The recovery of hormone binding starts on the 2nd day after HCG treatment, rises slightly between days 2 and 6, and repidly between days 7 and 8. The reappearance of free receptor sites can be suppressed by bromocriptine between days 7 and 8, but not before day 6 after the HCG injection indicating a different regulation of these receptors. The bromocriptine refractory reappearance of hormone binding between days 2 and 6 might be due to receptors of non-luteal cells, possibly by dissociation of the hormone-receptor complexes. The sum of occupied and free receptors is nearly identical during this time. In contrast, the increase of binding capacity between days 7 and 8 depends on a de novo synthesis of luteal cell receptors. These findings clearly demonstrate that the LH/HCG receptor in luteinized cells is only used once and degraded after the interaction with the hormone.

Key words

Ovary Luteinizing and human chorion-gonadotropic hormone Luteal cell receptors Receptor loss Receptor regulation 

Zusammenfassung

Rattenovarien enthalten am 16. Tag der Schwangerschaft eine hohe Konzentration an LH/HCG-Rezeptoren. Nach der Gabe von 200 IE HCG verlieren die Ovar-Membranen nahezu vollständig die Fähigkeit125I-HCG zu binden. Die Bestimmung der besetzten Rezeptoren zeigt, daß der anfängliche Verlust Hormon zu binden mit der Besetzung der Rezeptoren einhergeht, daß aber die anhaltende Verminderung der Bindungskapazität nicht auf die Rezeptor-Besetzung zurückgeführt werden kann. Vier Tage nach der Hormongabe ist im Ovar nahezu kein Hormon mehr nachweisbar. Erneute Bindungsfähigkeit ist ab dem 2. Tag nach der Hormongabe zu sehen. Zwischen dem 2. und 6. Tag steigt sie langsam zwischen dem 7. und 8. Tag dagegen äußerst schnell an. Die Zunahme freier Rezeptoren zwischen dem 7. und 8. Tag kann durch die Gabe von Bromocriptin verhindert werden, nicht jedoch das Wiederauftreten von Rezeptoren bis zum 6. Tag nach der Hormongabe. Aus diesem Verhalten wird eine unterschiedliche Regulation der Rezeptoren ersichtlich. Das Bromocriptin-refraktäre Wiederauftreten von Rezeptoren zwischen dem 2. und 6. Tag ist auf Rezeptoren ausschließlich nicht-lutealer Zellen zurückzuführen, möglicherweise durch Dissoziation des Rezeptor-Hormon-Komplexes. Die Summe besetzter und freier Rezeptoren während dieses Zeitraumes ist nahezu identisch. Im Gegensatz dazu beruht die zunehmende Bindungskapazität zwischen dem 7. und 8. Tag auf einer Neusynthese von Rezeptoren in Luteal-Zellen. Diese Befunde zeigen, daß der LH/HCG-Rezeptor in luteinisierten Zellen nur einmal verwendungsfähig ist und nach der hormonalen Interaktion abgebaut wird.

Schlüsselwörter

Ovar luteinisierendes und choriongonadotropes Hormon Luteal-Zell-Rezeptor Rezeptor-Verlust Rezeptor-Regulation 

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Copyright information

© J. F. Bergmann Verlag 1980

Authors and Affiliations

  • U. Müller
    • 1
  • Th. Bauknecht
    • 2
  • J. W. Siebers
    • 2
  1. 1.Institut für Humangenetik und Anthropologie der UniversitätFreiburg i. Br.Germany
  2. 2.Universitäts-FrauenklinikFreiburg i. Br.Germany

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