Evidence for different gonadotropin-releasing hormone response sites in rat ovarian and pituitary cells.

Biol Reprod

Laboratorio de Neuroendocrinología, Instituto de Biología y Medicina Experimental (IBYME), 1428 Buenos Aires, Argentina.

Published: August 2004

AI Article Synopsis

  • The study explored how the type I GnRH receptor regulates gonadotropin secretion in rat pituitary cells when exposed to GnRH-II.
  • GnRH-II was found to stimulate the release of LH and FSH in a dose-dependent manner, while the GnRH-analog 135-18 did not trigger any cellular response.
  • In ovarian cells, GnRH-I was effective in inducing a response, unlike GnRH-II; however, both peptides showed antiproliferative effects, with 135-18 having a greater impact on cell proliferation and increasing progesterone secretion.

Article Abstract

The participation of type I GnRH receptor (GnRH-R) on GnRH-II-induced gonadotropin secretion in rat pituitary cells was investigated. Furthermore, we extended the study of GnRH-II action to ovarian cells. The GnRH-II was able to mobilize inositol triphosphate (IP(3)) and to induce LH and FSH release in a dose-dependent manner in pituitary cells and in a GnRH-I-like manner. The GnRH-analog 135-18 (agonist for type II GnRH-R and antagonist for type I GnRH-R) was unable to elicit any cellular response tested in these pituitary cells. The GnRH-II responses were blocked by the type I GnRH-R-antagonists CRX or 135-18, suggesting that these effects were mediated by the type I GnRH-R. In contrast to pituitary cells, GnRH-I, but not GnRH-II, elicited an IP(3) response in superovulated ovarian cells; 135-18 also had no effect. However, GnRH-II as well as GnRH-I presented antiproliferative effects on these cells. Surprisingly, 135-18 had stronger antiproliferative effects than either GnRH peptide. The 135-18 analog, but not GnRH-I or GnRH-II, increased progesterone secretion in superovulated ovarian cells. These results strongly suggest that GnRH-II is able to stimulate rat pituitary cells through the type I GnRH-R, with no evidence for the presence of type II GnRH-R. On the other hand, our results indicate a putative GnRH-R in superovulated ovarian cells with response characteristics that differ from those of the GnRH-R in the pituitary.

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http://dx.doi.org/10.1095/biolreprod.104.027342DOI Listing

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