title: A chronic low dose infusion of insulin-like growth factor I alters placental function but does not affect fetal growth.
abstract: Knowledge of the anabolic effects of insulin-like growth factor I (IGF-I) on fetal growth and feto-placental metabolism are derived from studies using large doses of IGF-I. Low doses of enteral IGF-I have trophic effects on the fetal gut, but there are no data on the effects of systemic low doses of IGF-I on fetal growth and feto-placental metabolism. We therefore compared the effects of a chronic infusion of low dose IGF-I (50 microg day(-1), n = 7) with vehicle-infused controls (n = 7) on fetal growth, metabolism and placental transfer capacity in the chronically instrumented late gestation ovine fetus (121-132 days of gestation; term = 145 days). Insulin-like growth factor I infusion did not affect fetal growth or the size of individual organs, including liver, spleen and bone. Placental morphology was altered, and placental clearances of 3-O-[methyl-3H]D-glucose (a non-metabolizable glucose analogue) and [methyl(14C)]aminoisobutyric acid (a non-metabolizable analogue of amino acids utilizing the system A transporter), were reduced in IGF-I-treated fetuses (P < 0.05 v. control). However, fetal and placental metabolite uptake was not significantly different between groups. We conclude that, despite altering placental transfer capacity and morphology, a chronic low dose infusion of IGF-I does not alter fetal growth or metabolism.
authors.affiliation: Liggins Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Frank H
authors.initials: FH
authors.lastname: Bloomfield
authors.forename: Pierre L
authors.initials: PL
authors.lastname: van Zijl
authors.forename: Michael K
authors.initials: MK
authors.lastname: Bauer
authors.forename: Jane E
authors.initials: JE
authors.lastname: Harding
mesh_terms: D019325:3-O-Methylglucose; D000818:Animals; D001783:Blood Flow Velocity; D001842:Bone and Bones / Q000196:embryology; D002245:Carbon Dioxide / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005314:Embryonic and Fetal Development / Q000187:drug effects*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005333:Fetus / Q000098:blood supply / Q000378:metabolism; D005865:Gestational Age; D006863:Hydrogen-Ion Concentration; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage* / Q000032:analysis; D008099:Liver / Q000196:embryology; D008297:Male; D009929:Organ Size; D010100:Oxygen / Q000097:blood; D010920:Placenta / Q000098:blood supply / Q000187:drug effects* / Q000502:physiology*; D011247:Pregnancy; D012756:Sheep; D013154:Spleen / Q000196:embryology; D015091:beta-Alanine / Q000031:analogs & derivatives*
chemical_list: D015091:beta-Alanine; D002245:Carbon Dioxide; D019325:3-O-Methylglucose; C012924:2,2-dimethyl-beta-alanine; D007334:Insulin-Like Growth Factor I; D010100:Oxygen