Ontogeny of placental lactogen-I and placental lactogen-II expression in the developing rat placenta.
The purpose of this investigation was to identify the cellular origin, and the temporal and regional characteristics of placental lactogen-I (PL-I) and placental lactogen-II (PL-II) expression during placental development in the rat. PL-I and PL-II mRNA expression were assessed by Northern blot analysis and in situ hybridization. PL-I and PL-II protein expression were determined by Western blot and immunocytochemical analyses. PL-I mRNA was first detected by in situ hybridization at Day 6 of gestation in mural trophoblast giant cells and a day later, PL-I protein was first detected by immunocytochemistry. PL-I immunostaining extended to the polar trophoblast giant cells as gestation advanced. Polar trophoblast giant cell staining for PL-I was not as intense as the mural trophoblast giant cell staining. Northern and Western blot analyses confirmed the asymmetric distribution of PL-I expression. PL-I mRNA migrated as a 1-kb species and PL-I protein migrated as 30- and 36-40-kDa forms. PL-I expression abruptly declined at Day 12, and by Day 13, PL-I was not detectable. PL-II protein was first detectable at Day 11 of gestation and was localized to trophoblast giant cells. PL-II mRNA could be detected at Day 10 of gestation. Northern and Western blot analyses indicated that PL-II expression significantly increased as gestation advanced and that PL-II expression was asymmetrically distributed similar to PL-I. PL-II mRNA migrated as a 1-kb species and PL-II protein migrated as a 25-kDa species. Blastocysts recovered on Day 4 of gestation initially showed no detectable expression of PL-I or PL-II; however, after 2 days of culture PL-I protein expression was detectable. Biochemical characteristics of PL-I synthesized and secreted by blastocyst outgrowths were similar to PL-I synthesized and secreted by Day 10 placental explants. In summary, (1) PL-I and PL-II are produced by trophoblast giant cells of the developing placenta, (2) PL-I and PL-II exhibit distinct temporal and regional patterns of expression during placental morphogenesis, and (3) PL-I expression by blastocyst outgrowths can be induced in vitro, whereas a more complex array of signals appears necessary for induction of PL-II expression.
Department of Physiology, University of Kansas Medical Center, Kansas City 66103.
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Faria
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Kwok
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Talamantes
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Soares
D000482:Allantois / Q000166:cytology / Q000502:physiology; D000818:Animals; D001755:Blastocyst / Q000502:physiology; D015152:Blotting, Northern; D015153:Blotting, Western; D002823:Chorion / Q000166:cytology / Q000502:physiology; D004247:DNA / Q000235:genetics; D005260:Female; D009693:Nucleic Acid Hybridization; D010920:Placenta / Q000166:cytology / Q000502:physiology*; D010928:Placental Lactogen / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics*; D051381:Rats; D014817:Vitelline Membrane / Q000166:cytology / Q000502:physiology
D012333:RNA, Messenger; D004247:DNA; D010928:Placental Lactogen