title: Hormonal regulation of glucose and system A amino acid transport in first trimester placental villous fragments.
abstract: Alterations in placental nutrient transfer have been implicated in fetal growth abnormalities. In pregnancies complicated by diabetes and accelerated fetal growth, upregulations of glucose transporter 1 (GLUT1) and amino acid transporter system A have been shown in the syncytiotrophoblast of term placenta. In contrast, intrauterine growth restriction is associated with a downregulation of placental system A transporters. However, underlying mechanisms of transporter regulation are poorly understood, particularly in early pregnancy. In this study, hormonal regulation of placental glucose and system A transporters was investigated. The uptake of 3-O-[methyl-(14)C]-d-glucose was studied in villous fragments isolated from first trimester (6-13 wk of gestation) and term human placenta. Villous fragments were incubated in buffer containing insulin, leptin, cortisol, growth hormone (GH), prolactin, IGF-I, or under hypo/hyperglycemic conditions for 1 h. Subsequently, 3-O-[methyl-(14)C]-D-glucose uptake was measured with and without phloretin for 70 s in first trimester tissue and 20 s in term tissue. Methylaminoisobutyric uptake was measured with and without Na+ for 20 min. Glucose uptake was unaltered by hormones or hypo/hyperglycemia. GH decreased system A activity by 31% in first trimester (P < 0.05). The uptake of glucose was 50% higher in term compared with first trimester fragments and increased markedly between 6 and 13 wk of gestation (P < 0.05). We conclude that placental glucose transporter activity is not regulated by short exposures to the hormones or glucose concentrations tested. In contrast to term placental villous fragments, system A activity was not regulated by insulin or leptin in first trimester but was downregulated by GH.
authors.affiliation: Perinatal Center, Dept. of Physiology and Pharmacology, Göteborg University, Box 432, 405 30 Göteborg, Sweden. anette.ericsson@fysiologi.gu.se
authors.forename: Anette
authors.initials: A
authors.lastname: Ericsson
authors.forename: Bengt
authors.initials: B
authors.lastname: Hamark
authors.forename: Nina
authors.initials: N
authors.lastname: Jansson
authors.forename: Bengt R
authors.initials: BR
authors.lastname: Johansson
authors.forename: Theresa L
authors.initials: TL
authors.lastname: Powell
authors.forename: Thomas
authors.initials: T
authors.lastname: Jansson
mesh_terms: D026924:Amino Acid Transport System A / Q000378:metabolism*; D002824:Chorionic Villi / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D005865:Gestational Age; D005947:Glucose / Q000378:metabolism; D006728:Hormones / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009994:Osmolar Concentration; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D013997:Time Factors; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
chemical_list: D026924:Amino Acid Transport System A; D006728:Hormones; D009004:Monosaccharide Transport Proteins; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D005947:Glucose