Increase in Pit-1 mRNA Is Not Required for the Estrogen-Induced Expression of Prolactin Gene and Lactotroph Proliferation

Endocrine Journal

HISAO SEO²  YUTAKA TOMODA¹  NOBUHIKO SUGANUMA¹  SHIN-ICHIRO TSUKAHARA²  FUKUSHI KAMBE² 

[1] Department of Obstetrics and Gynecology, School of Medicine, Nagoya University;Department of Endocrinology and Metabolism, Division of Molecular and Cellular Adaptation, Research institute of Environmental Medicine, Nagoya University

关键词: Pit-1;    Prolactin;    Estrogen;    Rat;   

DOI  :  10.1507/endocrj.41.579

学科分类：内分泌与代谢学

来源: Japan Endocrine Society

【 摘 要 】

References(28)Cited-By(2)Estrogen has been shown to stimulate lactotroph proliferation and expression of the prolactin (PRL) gene. Recently it has been established that Pit-1, a pituitary-specific transcription factor, is required for lactotroph proliferation. Furthermore, in vitro studies showed that an increase in the PRL promoter activity caused by estrogen was dependent of the amount of cotransfected Pit-1-expressing plasmid. These findings led us to examine whether the induction of Pit-1 mRNA is required for the estrogen-increased PRL gene expression in the rat anterior pituitary in vivo. Short term estrogen treatment was achieved by means of a single intramuscular injection of estradiol dipropionate. DNA synthesis, the levels of PRL and Pit-1 messenger RNAs in the anterior pituitary were determined. Estradiol dipropionate resulted in a significant increase in DNA synthesis 24h after administration and in PRL mRNA after 48h. In contrast, the Pit-1 mRNA level was not altered. Since Pit-1 is expressed not only in lactotroph but also in somatotroph and thyrotroph, and the lactotroph cell population has been reported to be less than 10% in the pituitary, the change in the Pit-1 mRNA level in lactotrophs was not seen following only short term estrogen treatment. An increase in the lactotroph cell population was therefore achieved by chronic estrogen treatment (subcutaneous implantation of a silastic tube containing 17β-estradiol powder for 30 days). This treatment resulted in the marked proliferation of lactotrophs and a 3-fold increase in PRL mRNA. However, no alteration in Pit-1 mRNA was observed. These results suggest that the increase in Pit-1 mRNA is not required for the estrogen-induced lactotroph proliferation or PRL gene expression.

【 授权许可】

Unknown