Biology of Reproduction, Vol 41, 505-511, Copyright © 1989 by Society for the Study of Reproduction

ARTICLES

Gonadotropin-releasing hormone binding sites in ovaries of normal cycling and persistent-estrus rats

K Koves, PE Gottschall and A Arimura
U.S.-Japan Biomedical Research Laboratories, Tulane University Hebert Center, Belle Chase, Louisiana 70037.

The gonadotropin-releasing hormone (GnRH) binding capacity in ovaries and pituitaries of normal cycling rats at different stages of the estrous cycle and in ovaries of persistent-estrus rats was measured using radioligand-receptor assay (RRA). Persistent estrus was induced either by neonatal administration of testosterone propionate (1.25 mg s.c.) on the second day of life or by a hypothalamic suprachiasmatic frontal cut made with Halasz' knife. All animals were killed during the critical period (1400-1600 h), and GnRH receptor was assayed. GnRH receptor levels in both ovaries and pituitaries changed during the estrous cycle. The total number of ovarian GnRH binding sites was significantly higher in proestrus than in diestrus 1, the stage in which the lowest level was found. When binding sites were expressed in fmol/mg ovary, the highest level was observed in diestrus 2; however, no changes were observed during the estrous cycle when GnRH binding sites were expressed as fmol/mg protein. Changes noted were very similar to those demonstrated in pituitary GnRH receptors in our present and previous experiments. Higher levels of pituitary binding sites were found in diestrus 2 and proestrus than in estrus and diestrus 1. The changes in the GnRH receptor levels were more striking in the pituitary than in the ovaries. It appears that the total number of ovarian GnRH binding sites was not altered in either of the two persistent-estrus groups, but that their concentration was significantly higher (expressed in fmol/mg ovary or fmol/mg protein) than on any day during the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				P. Morales Gonadotropin-Releasing Hormone Increases Ability of the Spermatozoa to Bind to the Human Zona Pellucida Biol Reprod, August 1, 1998; 59(2): 426 - 430. [Abstract] [Full Text]