Up-regulation of pituitary [125I]insulin-like growth factor-I (IGF-I) binding and IGF binding protein-2 and IGF-I gene expression by estrogen

Kathleen M. Michels, Wei Hua Lee, Alicia Seltzer, Juan M. Saavedra, Carolyn A. Bondy

Research output: Contribution to journalArticle

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Abstract

To evaluate the effects of estrogen on the rat pituitary insulin-like growth factor (IGF) system, binding of [125I]IGF-I and in situ hybridization for IGF-I, the IGF-I receptor and IGF binding protein-2 (IGFBP-2) were coupled with quantitative autoradiography. The groups included intact cycling females, intact males, and gonadectomized males and females with or without estrogen pellet implants. Binding of [125I] IGF-I in the anterior lobe of the pituitary occurred in dense clusters over a diffuse lower density background. [125I]IGF-I binding was significantly increased in the estrogen-treated groups and was highest at proestrus compared to the rest of the estrous cycle. IGF-I receptor messenger RNA (mRNA) was distributed diffusely through the anterior pituitary and was not different between the respective gonadectomized and estrogen-treated groups. IGFBP-2 mRNA was clustered throughout the anterior pituitary and was significantly higher in the estrogen-treated groups as noted above for [125I]IGF-I binding. IGF-I mRNA was diffuse throughout the anterior pituitary and was also significantly higher in the estrogen-treated groups. In the neural lobe, [125I]IGF-I binding, IGFBP-2 mRNA, IGF-I receptor mRNA, and IGF-I mRNA were all uniformly distributed and did not differ between groups. The results show that circulating estrogen differentially regulates components of the pituitary IGF-I system in a region-specific manner and suggest that a portion of IGF binding in the anterior pituitary may be to IGFBP-2.

Original languageEnglish (US)
Pages (from-to)23-29
Number of pages7
JournalEndocrinology
Volume132
Issue number1
StatePublished - Jan 1993
Externally publishedYes

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Insulin-Like Growth Factor Binding Protein 2
Insulin-Like Growth Factor I
Estrogens
Up-Regulation
Gene Expression
IGF Type 1 Receptor
Messenger RNA
Somatomedins
Posterior Pituitary Gland
Proestrus
Anterior Pituitary Gland
Estrous Cycle
Autoradiography
In Situ Hybridization

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Up-regulation of pituitary [125I]insulin-like growth factor-I (IGF-I) binding and IGF binding protein-2 and IGF-I gene expression by estrogen. / Michels, Kathleen M.; Lee, Wei Hua; Seltzer, Alicia; Saavedra, Juan M.; Bondy, Carolyn A.

In: Endocrinology, Vol. 132, No. 1, 01.1993, p. 23-29.

Research output: Contribution to journalArticle

Michels, Kathleen M. ; Lee, Wei Hua ; Seltzer, Alicia ; Saavedra, Juan M. ; Bondy, Carolyn A. / Up-regulation of pituitary [125I]insulin-like growth factor-I (IGF-I) binding and IGF binding protein-2 and IGF-I gene expression by estrogen. In: Endocrinology. 1993 ; Vol. 132, No. 1. pp. 23-29.
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