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RESEARCH-ARTICLE |
C Wright, Biomedical Sciences, Colorado State University, Fort Collins, United States
R Orbus, Biomedical Sciences, Colorado State University, Fort Collins, United States
T Regnault, Pediatrics, University of Colorado, Aurora, United States
R Anthony, Department of Physiology, Colorado State University, Fort Collins, 80523-1683, United States
Correspondence: Russ Anthony, Email: russ.anthony{at}colostate.edu
Abstract
Ovine growth hormone (oGH) is synthesized in placental tissue during maximal placental growth and development. Our objectives were to localize oGH mRNA in the placenta, and study the impact of exogenous GH on twin pregnancies during the normal window (35-55 days gestational age; dGA) of placental expression. In situ hybridization localized oGH mRNA in uterine luminal epithelium and no tissues of fetal origin. While maternal GH and insulin-like growth factor (IGF) -1 concentrations were increased (P<0.001) approximately 10-fold, uterine, uterine fluid, placental and fetal weights were unaffected by treatment at either 55 or 135 dGA. Fetal length, liver weight, and liver weight per kg of body weight were unaffected by maternal GH treatment. However, in the cotyledon, IGF binding protein (BP)-1 and IGF BP-4 mRNA concentrations were increased (P < 0.05), while IGF BP-2 mRNA was decreased (P < 0.05). Concentrations of mRNA for IGF BP-3 was unaffected by treatment. Within the caruncle, IGF BP-1 mRNA was decreased (P < 0.05), while IGF BP-3 and IGF BP-4 mRNA were increased (P < 0.05), and IGF BP-2 mRNA was unchanged due to GH treatment. While our data indicate that elevated maternal GH and IGF-1 concentrations during early- and mid-gestation do not enhance placental and fetal growth in twin pregnancies, localization of GH mRNA in uterine luminal epithelium could explain GHs transitory expression from 35 to 55 dGA, since by the end of this period the majority of the uterine luminal epithelium has fused with chorionic binucleate cells forming the placental syncytium.
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