Receptors for chorionic gonadotropin in the corpus luteum of the rhesus monkey during simulated early pregnancy: Lack of down-regulation

J. S. Ottobre, Richard Stouffer

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Stimulation of the primate corpus luteum (CL) by endogenous CG in early pregnancy or by exogenous hCG in simulated early pregnancy is transient, possibly due to a drop in the number of available gonadotropin receptors in the CL. The objective of the current study was to determine if this reduction in available CG receptors in the CL is due to down-regulation of the total receptor population or occupation of receptors by CG. CL were removed from rhesus monkeys (n=27) during prolonged CG exposure in simulated early pregnancy. Luteal tissue was homogenized, and a particulate preparation (20,000 g) was formed. Bound gonadotropin was eluted from half of each tissue preparation with 0.05 M Na acetate-HCl in 0.1% gelatin (pH 3.3); the other half was treated with control buffer (0.05 M Tris-HCl, pH7.4). The hCG in the eluate was quantified by RIA and used to estimate the number of occupied receptors. Numbers and affinities of receptors were estimated by Scatchard analyses of specific [125I]hCG binding. Serum concentrations of progesterone increased within 9 h of hCG treatment and declined between 3 and 10 days of treatment. Whereas the number of available receptors declined from 0 h to 10 days of hCG treatment, the number of receptors occupied by hCG increased throughout treatment from 0.19 ± 0.01 fmol/mg tissue (mean ± SE) after 2 h of treatment to 7.76 ± 1.73 fmol/mg after 10 days of treatment (P0.10). The dissociation constants (K(d)) for CG binding were greater (P-10 M) and 10 days (5.24 ± 0.54 x 10-10 M) of treatment than after 0-3 days (0.95 ± 0.06 x 10-10 M) of treatment. Notably, the percentage of total receptors able to rebind hCG after elution declined from 0 h (79.0 ± 5.4%) to 10 days (23.0 ± 3.2%; P

Original languageEnglish (US)
Pages (from-to)1594-1602
Number of pages9
JournalEndocrinology
Volume119
Issue number4
StatePublished - 1986
Externally publishedYes

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LH Receptors
Corpus Luteum
Macaca mulatta
Down-Regulation
Pregnancy
Gonadotropin Receptors
Gelatin
Gonadotropins
Occupations
Primates
Progesterone
Buffers
Acetates
Serum
Population

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

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title = "Receptors for chorionic gonadotropin in the corpus luteum of the rhesus monkey during simulated early pregnancy: Lack of down-regulation",
abstract = "Stimulation of the primate corpus luteum (CL) by endogenous CG in early pregnancy or by exogenous hCG in simulated early pregnancy is transient, possibly due to a drop in the number of available gonadotropin receptors in the CL. The objective of the current study was to determine if this reduction in available CG receptors in the CL is due to down-regulation of the total receptor population or occupation of receptors by CG. CL were removed from rhesus monkeys (n=27) during prolonged CG exposure in simulated early pregnancy. Luteal tissue was homogenized, and a particulate preparation (20,000 g) was formed. Bound gonadotropin was eluted from half of each tissue preparation with 0.05 M Na acetate-HCl in 0.1{\%} gelatin (pH 3.3); the other half was treated with control buffer (0.05 M Tris-HCl, pH7.4). The hCG in the eluate was quantified by RIA and used to estimate the number of occupied receptors. Numbers and affinities of receptors were estimated by Scatchard analyses of specific [125I]hCG binding. Serum concentrations of progesterone increased within 9 h of hCG treatment and declined between 3 and 10 days of treatment. Whereas the number of available receptors declined from 0 h to 10 days of hCG treatment, the number of receptors occupied by hCG increased throughout treatment from 0.19 ± 0.01 fmol/mg tissue (mean ± SE) after 2 h of treatment to 7.76 ± 1.73 fmol/mg after 10 days of treatment (P0.10). The dissociation constants (K(d)) for CG binding were greater (P-10 M) and 10 days (5.24 ± 0.54 x 10-10 M) of treatment than after 0-3 days (0.95 ± 0.06 x 10-10 M) of treatment. Notably, the percentage of total receptors able to rebind hCG after elution declined from 0 h (79.0 ± 5.4{\%}) to 10 days (23.0 ± 3.2{\%}; P",
author = "Ottobre, {J. S.} and Richard Stouffer",
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