Inhibitory effect of a highly potent antagonist of LH releasing hormone (SB-75) on the pituitary gonadal axis in the intact and castrated rat

Daniel Ayalon, Yakob Farhi, Anna Maria Comaru-Schaliy, Andrew Victor Schally, Nachman Eckstein, Israel Vagman, Rona Limor

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

The biological potency of the new, highly potent antagonist [AC-D-Nal (2)1, D-Phe(4Cl)2, D-Pal(3)3, D-Cit6, D-Ala10] LH-RH (SB-75) on the pituitary-gonadal system of female castrated and intact ovulating rats was tested. Administration of a single dose (50-100 μg/kg BW) of the antagonist SB-75 inhibited effectively the elevated gonadotrophin levels for 48 h. Pituitary LH and FSH content was not affected by SB-75 treatment. When administered in the early afternoon of the proestrus to intact cycling rats, SB-75 blocked the preovulatory LH surge as well as the primary and secondary FSH surges. However, the secondary FSH surge was not affected by SB-75 treatment when administered on the evening of proestrus suggesting its independence from the LH-RH mechanism. A group of ovariectomized rats was chronically treated with D-Trp6-LH-RH after having been pretreated by administration of a single dose of the antagonist. The initial stimulatory release of LH and FSH initiated by injection of the LH-RH agonist was significantly reduced by pretreatment with the LH-RH antagonist. We conclude that the LH-RH antagonist SB-75 may be used effectively in the field of reproductive dysfunction and endocrinological oncology and may become an invaluable physiological probe in studying the hormonal dynamics of the reproductive endocrine axis.

Original languageEnglish (US)
Pages (from-to)153-159
Number of pages7
JournalNeuroendocrinology
Volume58
Issue number2
DOIs
StatePublished - Jan 1 1993
Externally publishedYes

Keywords

  • Follicle-stimulating hormone
  • Luteinizing hormone
  • Luteinizing-hormone-releasing hormone antagonist
  • Ovariectomy

ASJC Scopus subject areas

  • Endocrinology
  • Neuroscience(all)

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