title: Involvement of insulin-like growth factor-I for the regulation of prolactin synthesis by estrogen and postnatal proliferation of lactotrophs in the mouse anterior pituitary.
abstract: Estradiol (E2) stimulates not only secretion of prolactin (PRL) and proliferation of PRL-producing cells (PRL cells) in the anterior pituitary, but also the expression of growth factors. In insulin-like growth factor-I (IGF-I) knockout (KO) mice, the number of PRL cells is decreased and administration of IGF-I does not increase either the number of PRL cells or plasma PRL levels, indicating that IGF-I plays a pivotal role in PRL cells. The effect of E2 on PRL cells in KO mice was investigated by immunohistochemistry and real-time RT-PCR. The number of PRL cells in KO mice was significantly lower than in the wild-type (WT) control mice. E2 increased the PRL mRNA in WT and KO mice; however, an increase of PRL mRNA in KO was less than that in WT. In addition, no vasoactive intestinal peptide (VIP)-immunoreactive cells were found in KO mice, therefore IGF-I is essential for VIP expression. To investigate the roles of IGF-I on PRL cells in the postnatal development, double-immunostaining with PRL and BrdU was performed in WT and KO mice from days 5-20. The percentages of PRL cells and BrdU-labeled cells in the anterior pituitary of KO mice were lower than in WT mice. Thus, IGF-I may be responsible for proliferation and differentiation of PRL cells in this postnatal period. Differentiation and the proliferation of PRL cells are controlled by IGF-I during the postnatal development, and IGF may be a mediator of E2 action through VIP induction in PRL cells of adults.
authors.affiliation: Graduate School of Integrated Science, Yokohama City University, Yokohama, 236-0027, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Saitoh
authors.forename: Tamiki
authors.initials: T
authors.lastname: Hikake
authors.forename: Shinji
authors.initials: S
authors.lastname: Hayashi
authors.forename: Taisen
authors.initials: T
authors.lastname: Iguchi
authors.forename: Tomomi
authors.initials: T
authors.lastname: Sato
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001973:Bromodeoxyuridine; D002452:Cell Count / Q000639:trends; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D004958:Estradiol / Q000378:metabolism* / Q000494:pharmacology; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D052682:Lactotrophs / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D011388:Prolactin / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D014660:Vasoactive Intestinal Peptide; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D001973:Bromodeoxyuridine