Hormonal regulation of glucose and system A amino acid transport in first trimester placental villous fragments.
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.
Ericsson
Anette
A
Perinatal Center, Dept. of Physiology and Pharmacology, Göteborg University, Box 432, 405 30 Göteborg, Sweden. anette.ericsson@fysiologi.gu.se
Hamark
Bengt
B
Jansson
Nina
N
Johansson
Bengt R
BR
Powell
Theresa L
TL
Jansson
Thomas
T
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
D026924:Amino Acid Transport System A; D006728:Hormones; D009004:Monosaccharide Transport Proteins; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D005947:Glucose