17beta-estradiol induced vitellogenesis is inhibited by cortisol at the post-transcriptional level in Arctic char ( Salv
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17beta-estradiol induced vitellogenesis is inhibited by cortisol at the post-transcriptional level in Arctic char (Salvelinus alpinus) Hakan Berg1,2, Carina Modig3 and Per-Erik Olsson*1,3 Address: 1Department of Molecular Biology, Umea University, Umea, Sweden, 2Department of Marine Science, University of Texas Marine Science Institute, University of Texas, Port Aransas, Texas, USA and 3Department of Natural Science, Unit of Molecular Biology, Orebro University, Orebro, Sweden Email: Hakan Berg - [email protected]; Carina Modig - [email protected]; Per-Erik Olsson* - [email protected] * Corresponding author
Published: 02 September 2004 Reproductive Biology and Endocrinology 2004, 2:62
doi:10.1186/1477-7827-2-62
Received: 06 April 2004 Accepted: 02 September 2004
This article is available from: http://www.rbej.com/content/2/1/62 © 2004 Berg et al; licensee BioMed Central Ltd. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract This study was performed to investigate stress effects on the synthesis of egg yolk precursor, vitellogenin (Vtg) in Arctic char (Salvelinus alpinus). In particular the effect of cortisol (F) was determined since this stress hormone has been suggested to interfere with vitellogenesis and is upregulated during sexual maturation in teleosts. Arctic char Vtg was purified and polyclonal antibodies were produced in order to develop tools to study regulation of vitellogenesis. The Vtg antibodies were used to develop an enzyme-linked immunosorbent assay. The corresponding Vtg cDNA was cloned from a hepatic cDNA library in order to obtain DNA probes to measure Vtg mRNA expression. Analysis of plasma from juvenile Arctic char, of both sexes, exposed to different steroids showed that production of Vtg was induced in a dose dependent fashion by 17β-estradiol (E2), estrone and estriol. Apart from estrogens a high dose of F also upregulated Vtg. In addition, F, progesterone (P) and tamoxifen were tested to determine these compounds ability to modulate E2 induced Vtg synthesis at both the mRNA and protein level. Tamoxifen was found to inhibit E2 induced Vtg mRNA and protein upregulation. P did not alter the Vtg induction while F reduced the Vtg protein levels without affecting the Vtg mRNA levels. Furthermore the inhibition of Vtg protein was found to be dose dependent. Thus, the inhibitory effect of F on Vtg appears to be mediated at the post-transcriptional level.
Introduction The major proteinaceous egg yolk precursor vitellogenin (Vtg) is a large complex lipoglycophosphoprotein produced under estrogenic control in the liver of sexually maturing female oviparous animals. The estrogenic control of Vtg is mediated by binding of the most potent estrogen, 17-β-estradiol (E2), to the hepatic estrogen receptor (ER) [1].
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