The Capacity of the Antiestrogen CI-628 to Activate the Estrogen Receptor in Vitro

Willem D. De Boer, Angelo C. Notides, Benita S Katzenellenbogen, James R. Hayes, John A. Katzenellenbogen

Research output: Contribution to journalArticle

Abstract

The interactions of the antiestrogen CI-628 (α-[4-pyrrolidinoethoxy]phenyl-4-methoxy-α′- nitrostibene) with the cytoplasmic estrogen receptors from rat and calf uteri have been examined. The capacity of CI-628 to activate the estrogen receptor in vitro has been studied using three criteria previously established with the estradiol-receptor complex: 1) the biphasic dissociation kinetics of the estrogen-receptor complex, 2) the temperature- and hormone-dependent transformation of the receptor from a 4S to 5S sedimenting form, and 3) the translocation of the estrogen receptor from the cytoplasmic to the nuclear fraction of uterine tissue. The dissociation of [3H]CI-628 from the cytosol receptor at 0 C (t1/2 = 54 min) is 250-fold faster than the dissociation of estradiol and shows monophasic kinetics. Only a 2- to 3-fold decrease in the rate of the monophasic [3H]- CI-628 dissociation occurs after incubation under conditions sufficient to activate the estradiol-receptor complex. The rapid dissociation of [3H]CI-628 from the receptor causes a redistribution of label during sucrose gradient centrifugation. The true sedimentation profile of the receptor was determined by sedimenting the CI-628-receptor complex through a gradient containing unlabeled CI-628, followed by exchange of the receptorbound CI-628 for [3H]estradiol in the individual gradient fractions. Using this method, the cytoplasmic CI-628-receptor complex sediments in low salt gradients as an 8S species, as does the estradiol-receptor complex. In high salt gradients, the nonactivated CI-628-receptor complex sediments as a 4S species; warming to effect transformation does not produce the 5S (activated) receptor. High concentrations of CI-628 (5-10 µM), compared to 20 nM estradiol, effect only a moderate translocation of the estrogen receptor to the nucleus of uterine tissue incubated in vitro. The nuclear CI-628-receptor complex sedimentation rate was 4S, indicative of the nonactivated form of the receptor. We suggest that the rapid rate of CI-628 dissociation from the receptor results in an exceedingly small quantity and short lifetime of the activated CI-628-receptor complex. Thus, in vitro, in the absence of metabolism, CI-628 occupies cytoplasmic receptor sites, yet is ineffective in inducing receptor activation; this may, in part, account for its antagonistic character.

Original languageEnglish (US)
Pages (from-to)206-212
Number of pages7
JournalEndocrinology
Volume108
Issue number1
DOIs
StatePublished - Jan 1981

Fingerprint

Nitromifene
Estrogen Receptor Modulators
Estrogen Receptors
Estradiol Receptors
Estradiol
In Vitro Techniques
Cytoplasmic and Nuclear Receptors
Salts

ASJC Scopus subject areas

  • Endocrinology

Cite this

The Capacity of the Antiestrogen CI-628 to Activate the Estrogen Receptor in Vitro. / De Boer, Willem D.; Notides, Angelo C.; Katzenellenbogen, Benita S; Hayes, James R.; Katzenellenbogen, John A.

In: Endocrinology, Vol. 108, No. 1, 01.1981, p. 206-212.

Research output: Contribution to journalArticle

De Boer, Willem D. ; Notides, Angelo C. ; Katzenellenbogen, Benita S ; Hayes, James R. ; Katzenellenbogen, John A. / The Capacity of the Antiestrogen CI-628 to Activate the Estrogen Receptor in Vitro. In: Endocrinology. 1981 ; Vol. 108, No. 1. pp. 206-212.
@article{628eaf12c6464e8bb17652e8af9f269c,
title = "The Capacity of the Antiestrogen CI-628 to Activate the Estrogen Receptor in Vitro",
abstract = "The interactions of the antiestrogen CI-628 (α-[4-pyrrolidinoethoxy]phenyl-4-methoxy-α′- nitrostibene) with the cytoplasmic estrogen receptors from rat and calf uteri have been examined. The capacity of CI-628 to activate the estrogen receptor in vitro has been studied using three criteria previously established with the estradiol-receptor complex: 1) the biphasic dissociation kinetics of the estrogen-receptor complex, 2) the temperature- and hormone-dependent transformation of the receptor from a 4S to 5S sedimenting form, and 3) the translocation of the estrogen receptor from the cytoplasmic to the nuclear fraction of uterine tissue. The dissociation of [3H]CI-628 from the cytosol receptor at 0 C (t1/2 = 54 min) is 250-fold faster than the dissociation of estradiol and shows monophasic kinetics. Only a 2- to 3-fold decrease in the rate of the monophasic [3H]- CI-628 dissociation occurs after incubation under conditions sufficient to activate the estradiol-receptor complex. The rapid dissociation of [3H]CI-628 from the receptor causes a redistribution of label during sucrose gradient centrifugation. The true sedimentation profile of the receptor was determined by sedimenting the CI-628-receptor complex through a gradient containing unlabeled CI-628, followed by exchange of the receptorbound CI-628 for [3H]estradiol in the individual gradient fractions. Using this method, the cytoplasmic CI-628-receptor complex sediments in low salt gradients as an 8S species, as does the estradiol-receptor complex. In high salt gradients, the nonactivated CI-628-receptor complex sediments as a 4S species; warming to effect transformation does not produce the 5S (activated) receptor. High concentrations of CI-628 (5-10 µM), compared to 20 nM estradiol, effect only a moderate translocation of the estrogen receptor to the nucleus of uterine tissue incubated in vitro. The nuclear CI-628-receptor complex sedimentation rate was 4S, indicative of the nonactivated form of the receptor. We suggest that the rapid rate of CI-628 dissociation from the receptor results in an exceedingly small quantity and short lifetime of the activated CI-628-receptor complex. Thus, in vitro, in the absence of metabolism, CI-628 occupies cytoplasmic receptor sites, yet is ineffective in inducing receptor activation; this may, in part, account for its antagonistic character.",
author = "{De Boer}, {Willem D.} and Notides, {Angelo C.} and Katzenellenbogen, {Benita S} and Hayes, {James R.} and Katzenellenbogen, {John A.}",
year = "1981",
month = "1",
doi = "10.1210/endo-108-1-206",
language = "English (US)",
volume = "108",
pages = "206--212",
journal = "Endocrinology",
issn = "0013-7227",
publisher = "The Endocrine Society",
number = "1",

}

TY - JOUR

T1 - The Capacity of the Antiestrogen CI-628 to Activate the Estrogen Receptor in Vitro

AU - De Boer, Willem D.

AU - Notides, Angelo C.

AU - Katzenellenbogen, Benita S

AU - Hayes, James R.

AU - Katzenellenbogen, John A.

PY - 1981/1

Y1 - 1981/1

N2 - The interactions of the antiestrogen CI-628 (α-[4-pyrrolidinoethoxy]phenyl-4-methoxy-α′- nitrostibene) with the cytoplasmic estrogen receptors from rat and calf uteri have been examined. The capacity of CI-628 to activate the estrogen receptor in vitro has been studied using three criteria previously established with the estradiol-receptor complex: 1) the biphasic dissociation kinetics of the estrogen-receptor complex, 2) the temperature- and hormone-dependent transformation of the receptor from a 4S to 5S sedimenting form, and 3) the translocation of the estrogen receptor from the cytoplasmic to the nuclear fraction of uterine tissue. The dissociation of [3H]CI-628 from the cytosol receptor at 0 C (t1/2 = 54 min) is 250-fold faster than the dissociation of estradiol and shows monophasic kinetics. Only a 2- to 3-fold decrease in the rate of the monophasic [3H]- CI-628 dissociation occurs after incubation under conditions sufficient to activate the estradiol-receptor complex. The rapid dissociation of [3H]CI-628 from the receptor causes a redistribution of label during sucrose gradient centrifugation. The true sedimentation profile of the receptor was determined by sedimenting the CI-628-receptor complex through a gradient containing unlabeled CI-628, followed by exchange of the receptorbound CI-628 for [3H]estradiol in the individual gradient fractions. Using this method, the cytoplasmic CI-628-receptor complex sediments in low salt gradients as an 8S species, as does the estradiol-receptor complex. In high salt gradients, the nonactivated CI-628-receptor complex sediments as a 4S species; warming to effect transformation does not produce the 5S (activated) receptor. High concentrations of CI-628 (5-10 µM), compared to 20 nM estradiol, effect only a moderate translocation of the estrogen receptor to the nucleus of uterine tissue incubated in vitro. The nuclear CI-628-receptor complex sedimentation rate was 4S, indicative of the nonactivated form of the receptor. We suggest that the rapid rate of CI-628 dissociation from the receptor results in an exceedingly small quantity and short lifetime of the activated CI-628-receptor complex. Thus, in vitro, in the absence of metabolism, CI-628 occupies cytoplasmic receptor sites, yet is ineffective in inducing receptor activation; this may, in part, account for its antagonistic character.

AB - The interactions of the antiestrogen CI-628 (α-[4-pyrrolidinoethoxy]phenyl-4-methoxy-α′- nitrostibene) with the cytoplasmic estrogen receptors from rat and calf uteri have been examined. The capacity of CI-628 to activate the estrogen receptor in vitro has been studied using three criteria previously established with the estradiol-receptor complex: 1) the biphasic dissociation kinetics of the estrogen-receptor complex, 2) the temperature- and hormone-dependent transformation of the receptor from a 4S to 5S sedimenting form, and 3) the translocation of the estrogen receptor from the cytoplasmic to the nuclear fraction of uterine tissue. The dissociation of [3H]CI-628 from the cytosol receptor at 0 C (t1/2 = 54 min) is 250-fold faster than the dissociation of estradiol and shows monophasic kinetics. Only a 2- to 3-fold decrease in the rate of the monophasic [3H]- CI-628 dissociation occurs after incubation under conditions sufficient to activate the estradiol-receptor complex. The rapid dissociation of [3H]CI-628 from the receptor causes a redistribution of label during sucrose gradient centrifugation. The true sedimentation profile of the receptor was determined by sedimenting the CI-628-receptor complex through a gradient containing unlabeled CI-628, followed by exchange of the receptorbound CI-628 for [3H]estradiol in the individual gradient fractions. Using this method, the cytoplasmic CI-628-receptor complex sediments in low salt gradients as an 8S species, as does the estradiol-receptor complex. In high salt gradients, the nonactivated CI-628-receptor complex sediments as a 4S species; warming to effect transformation does not produce the 5S (activated) receptor. High concentrations of CI-628 (5-10 µM), compared to 20 nM estradiol, effect only a moderate translocation of the estrogen receptor to the nucleus of uterine tissue incubated in vitro. The nuclear CI-628-receptor complex sedimentation rate was 4S, indicative of the nonactivated form of the receptor. We suggest that the rapid rate of CI-628 dissociation from the receptor results in an exceedingly small quantity and short lifetime of the activated CI-628-receptor complex. Thus, in vitro, in the absence of metabolism, CI-628 occupies cytoplasmic receptor sites, yet is ineffective in inducing receptor activation; this may, in part, account for its antagonistic character.

UR - http://www.scopus.com/inward/record.url?scp=0019351257&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0019351257&partnerID=8YFLogxK

U2 - 10.1210/endo-108-1-206

DO - 10.1210/endo-108-1-206

M3 - Article

C2 - 7007019

AN - SCOPUS:0019351257

VL - 108

SP - 206

EP - 212

JO - Endocrinology

JF - Endocrinology

SN - 0013-7227

IS - 1

ER -