Rat ovarian insulin-like growth factor I (IGF-I) gene expression is granulosa cell-selective

5'-untranslated mRNA variant representation and hormonal regulation

E. R. Hernandez, Charles Roberts, D. LeRoith, E. Y. Adashi

Research output: Contribution to journalArticle

132 Citations (Scopus)

Abstract

We, and others, have recently reported that the ovary is a site of insulin-like growth factor (IGF)I gene expression. It was the objective of the present studies to assess the relative ovarian abundance of IGF-I transcripts with alternative 5'-untranslated (UT) regions, their cellular localization, and hormonal regulation. To this end, a solution hybridization/RNase protection assay was employed wherein total rat ovarian RNA was hybridized with a 404-base 32P-labelled rat IGF-I riboprobe corresponding to the Class A 5'UT variant. As in liver, three protected bands [322 (Class A), 297 (Class B), and 242 (Class C) bases long] were noted, in keeping with established alternative 5'UT transcripts. The ovarian (as the hepatic) Class C variant proved the most abundant. The ovarian Class B variant was barely detectable. Cellular localization studies revealed these ovarian IGF-I transcripts to be primarily, if not exclusively, of granulosa but not theca-interstitial cell origin. Treatment of immature (21-23 days old) hypophysectomized rats with a diethylstilbestrol (DES)-containing subcutaneous silastic implant for a total of 5 days resulted in a 2-fold increase in the (densitometrically quantified) abundance of ovarian IGF-I transcripts, a diametrically-opposed effect (2.6-fold decrease) being noted at the level of the liver. Whereas treatment of hypophysectomized rats with oGH by itself (150 μg, qd, sc 5 days) resulted in a 5-fold increase in hepatic IGF-I gene expression, a limited, albeit distinct inhibitory effect was observed on the steady-state levels of ovarian IGF-I mRNA. In contrast, combined treatment with oGH and DES yielded a 3-fold increase in the abundance of ovarian IGF-I transcripts, there being no net alteration in hepatic IGF-I gene expression. Taken together, these findings reveal ovarian expression of the 3 known 5'-UT IGF-I mRNA variants, document the granulosa cell as the main somatic ovarian cell of IGF-I mRNA generation, and indicate that hepatic and ovarian IGF-I gene expression are differentially regulated in diametrically opposed directions.

Original languageEnglish (US)
Pages (from-to)572-574
Number of pages3
JournalEndocrinology
Volume125
Issue number1
StatePublished - 1989
Externally publishedYes

Fingerprint

Granulosa Cells
Insulin-Like Growth Factor I
Gene Expression
Messenger RNA
Liver
Diethylstilbestrol
Theca Cells
5' Untranslated Regions
Ribonucleases
Ovary
RNA

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Rat ovarian insulin-like growth factor I (IGF-I) gene expression is granulosa cell-selective : 5'-untranslated mRNA variant representation and hormonal regulation. / Hernandez, E. R.; Roberts, Charles; LeRoith, D.; Adashi, E. Y.

In: Endocrinology, Vol. 125, No. 1, 1989, p. 572-574.

Research output: Contribution to journalArticle

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