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This Article Full Text Full Text (PDF) All Versions of this Article: JOE-09-0232v1 JOE-09-0232v2 203/2/231    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Hikake, T. Articles by Sato, T. PubMed PubMed Citation Articles by Hikake, T. Articles by Sato, T.

International Graduate School of Arts and Sciences, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027, Japan
¹ The Graduate University for Advanced Studies and Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki 444-8787, Japan

(Correspondence should be addressed to T Sato; Email: tomomi{at}yokohama-cu.ac.jp)

IGF1 knockout (IGF1KO) mice show a reduced number of prolactin (PRL) producing cells (PRL cells); however, the role of IGF1 in PRL cell proliferation and differentiation in immature mice is unclear. In this study, ontogenic changes in the percentages of PRL cells, GH producing cells (GH cells), and 5-bromo-2'-deoxyuridine (BrdU)-labeled cells in the anterior pituitary of male IGF1KO mice during the postnatal period were investigated. The percentage of PRL cells in IGF1KO mice was significantly lower at day 20 compared with that in wild-type (WT) mice, while GH cells in IGF1KO mice were significantly increased from day 10. From days 5 to 20, the percentage of BrdU-labeled cells in WT and IGF1KO mice was similar. PRL cells and GH cells are thought to originate from the same progenitor cells, therefore, PRL cells in IGF1KO mice are not able to differentiate because progenitor cells have already committed to be GH cells. However, IGF1, 17β-estradiol (E₂), epidermal growth factor (EGF), or IGF1 plus E₂ treatments increased the PRL cell number in the pituitaries in vitro of 10-day-old WT and IGF1KO mice. This fact suggests that these factors are involved in PRL cell proliferation and differentiation. In addition, the increase of PRL cells in IGF1KO mice stimulated by E₂ or EGF was less than that of WT mice. Thus, IGF1 plays a crucial role in PRL cell proliferation and differentiation in mouse pituitaries by regulating the differentiation of progenitor cells and mediating the actions of E₂ and EGF.