This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by LEE, C. Y. Articles by TAKAHASHI, H. Search for Related Content PubMed PubMed Citation Articles by LEE, C. Y. Articles by TAKAHASHI, H.

Follicle-Stimulating Hormone Receptors in Rat Ovaries: Decrease in Numbers of Binding Sites Associated with Luteinization

Department of Laboratory Medicine and Pathology, University of Minnesota Minneapolis, Minnesota 55455 Department of Molecular Medicine, Mayo Clinic and Mayo Foundation Rochester, Minnesota 55901

Abstract

Specific binding of human folliclestimulating hormone (hFSH) to receptors in aparticulate fraction of immature rat ovaries has been studied. The binding of human [125I]iodo-FSH is both timeand temperature-dependent and is a saturable process. Total binding amounted to 21% of the total radioactivity with 10 mg equivalent wt of ovary used. Nonspecific binding was very low (5% of total binding). Binding was competitively inhibited by unlabeled hFSH. Purified hLH and hLH- inhibited binding only at high concentrations, which was compatible with FSH contamination. Ovine prolactin and ovalbumin were without effect. No human [l25I]iodo-FSH was specifically bound by rat liver, intestine, spleen and kidney. The apparent dissociation constant of the hFSH-receptor complex was found to be 3.8 x 10^–10M. The effect of luteinization upon FSH binding activity of rat ovaries was also studied. The FSH binding capacity for the immature ovary was found to be 8.2 x 10^–16 mole/mg wt. During luteinization following a series of primings with oFSH and hCG, FSH receptor sites progressively decreased to 5.2 x 10^–16 mole/mg wt and 2.2 x 10¹⁶ mole/mg wt, respectively, after 5 and 7 injections. The receptor sites decreased further to undetectable levels in heavily luteinized ovaries following PMSG-hCG priming. The apparent dissociation constant of the human [I25I]iodo-FSH-binding site complex was not affected by the gonadotropin treatments. It is concluded that hCG-induced luteinization is associated with a decrease in number of FSH receptor sites and a loss of FSH-sensitive adenylate cyclase activity and that these changes may be important in the control of granulosa cell differentiation to luteal cells.

Footnotes

Supported by Grants from USPHS (HD 10075 and HD 9140).

Part of this work was presented at the 58th Annual Meeting of the Endocrine Society, San Francisco, California, June 23–25, 1976.

^* Present address: Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota 55455.

Received August 25, 1976.