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Study · In vitro (cell-free) · calf · 1982

3 results

The inhibition of the estrogen receptor's positive cooperative [3H]estradiol binding by the antagonist, clomiphene.

Sasson S, Notides AC

The Journal of biological chemistry1 Oct 1982Cited by 21 (Europe PMC)

PMID7118895 (opens in a new tab)DOI10.1016/s0021-9258(18)33795-5 (opens in a new tab)PepBankPUB-07118895
Publisher pagePubMedAsk about this study
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Summary

The calf uterine estrogen receptor showed positive cooperativity of [3H]estradiol equilibrium binding; the Scatchard plot was convex and the Hill coefficient was 1.69 +/- 0.021 (n = 14). The effects of the estrogenic antagonists, zuclomiphene (cis-2-(p-[2-chloro-1,2-diphenylvinyl]phenoxy)triethylamine citrate) and enclomiphene (trans-23-(p-[2-chloro-1,2-diphenylvinyl]phenoxy)triethylamine citrate), on the positive cooperativity of [3H]estradiol binding were measured by titrating the receptor with a variable concentration of [3H]estradiol and antagonist while maintaining a constant excess in a specific ratio of the antagonist to the [3H]estradiol. With a 45- to 55-fold molar excess of zuclomiphene or an 820- to 900-fold molar excess of enclomiphene above the [3H]estradiol concentration, the receptor's positive cooperative [3H]estradiol binding was inhibited. A transition from a convex to a linear Scatchard plot and a decrease in the Hill coefficient from 1.69 to 1.10 +/- 0.02 (n = 6) were induced. The specifically bound [3H]estradiol was inhibited 43 to 50% by the zuclomiphene and enclomiphene. The addition of unlabeled estradiol in a 1- or 2.3-fold molar excess above that of the [3H]estradiol concentration produced a 50 to 75% competitive displacement of the specifically bound [3H]estradiol; nevertheless, the Scatchard plot remained convex and the Hill coefficient was 1.74 and 1.80, respectively. Thus, inhibition of the positive cooperativity of [3H]estradiol binding by the clomiphene isomers was not due to dilution of the specifically bound [3H]estradiol by the antagonist. These data demonstrate that there are two molecular mechanisms by which an estrogen antagonist interferes with the function of the receptor: as a competitor, thus blocking the estrogen receptor's binding site to an agonist, and second by inducing conformational changes that inhibit site:site interactions and receptor activation.
CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study3

2 results from studies that gave the peptide. No result from this study comes from people.

  1. 01LabIn vitro (cell-free)Mechanism

    In calf uterine receptor assays, enclomiphene inhibited positive cooperative estradiol binding at an 820- to 900-fold molar excess.

    In plain wordsIn lab tests, enclomiphene inhibited cooperative estradiol binding to calf uterine estrogen receptors.

    Peptide
    Enclomiphene
    Outcome
    DecreasePositive cooperative estradiol binding
    Study

    calfn: not reported in source

    Calf uterine estrogen receptor
    Outcome group
    Receptor activity and mechanism · Pharmacology
    Studied dose
    820- to 900-fold molar excess above estradiolAs given in this study (calf).

    Source sentences

    Summary
    With a 45- to 55-fold molar excess of zuclomiphene or an 820- to 900-fold molar excess of enclomiphene above the [3H]estradiol concentration, the receptor's positive cooperative [3H]estradiol binding was inhibited.
  2. 02LabIn vitro (cell-free)Mechanism

    In calf uterine receptor assays, enclomiphene inhibited specifically bound estradiol by 43 to 50%.

    In plain wordsIn lab tests, enclomiphene reduced specifically bound estradiol by 43 to 50%.

    Peptide
    Enclomiphene
    Outcome
    DecreaseSpecifically bound estradiol
    Study

    calfn: not reported in source

    Calf uterine estrogen receptor
    Outcome group
    Receptor activity and mechanism · Pharmacology
    Studied dose
    Dose not stated

    Measurements

    Inhibition
    43 to 50%
    specifically bound estradiol

    Source sentences

    Summary
    The specifically bound [3H]estradiol was inhibited 43 to 50% by the zuclomiphene and enclomiphene.

Studies that did not test the peptide alone1

In this study, Enclomiphene was a lab tool or a carrier, part of a mix, or the subject of a lab method. These results are not evidence about taking Enclomiphene.

  1. 03LabNot a test of Enclomiphene aloneIn vitro (cell-free)Mechanism

    In calf receptor assays, clomiphene isomers including enclomiphene changed the Scatchard plot to linear and reduced the Hill coefficient.

    In plain wordsIn lab tests, clomiphene isomers including enclomiphene reduced receptor binding cooperativity.

    Peptide
    Enclomiphene
    Outcome
    DecreaseScatchard plot and Hill coefficient
    Study

    calfn = 6

    Calf uterine estrogen receptor
    Outcome group
    Receptor activity and mechanism · Pharmacology

    Measurements

    Hill coefficient
    1.69 unitless
    before inhibition
    Hill coefficient
    1.1 unitless
    after inhibition

    Source sentences

    Summary
    A transition from a convex to a linear Scatchard plot and a decrease in the Hill coefficient from 1.69 to 1.10 +/- 0.02 (n = 6) were induced.
    1 context sentence
    Summary · context
    With a 45- to 55-fold molar excess of zuclomiphene or an 820- to 900-fold molar excess of enclomiphene above the [3H]estradiol concentration, the receptor's positive cooperative [3H]estradiol binding was inhibited.

    In this study, Enclomiphene was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Enclomiphene.

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

  1. Version 2Current

    21 Oct 2026, 15:58 UTC

    Study results updated

  2. Version 1

    21 Oct 2026, 12:50 UTC

    First added · source update from Europe PMC

Subjects

Terms as the source lists them.

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