Time-dependent physiological regulation of ovine placental GLUT-3 glucose transporter protein.
We immunolocalized the GLUT-3 glucose transporter isoform versus GLUT-1 in the late-gestation epitheliochorial ovine placenta, and we examined the effect of chronic maternal hyperglycemia and hypoglycemia on placental GLUT-3 concentrations. GLUT-3 was limited to the apical surface of the trophoectoderm, whereas GLUT-1 was on the basolateral and apical surfaces of this cell layer and in the epithelial cells lining the placental uterine glands. GLUT-3 concentrations declined at 17-20 days of chronic hyperglycemia (P < 0.05), associated with increased uterine and uteroplacental net glucose uptake rate, but a normal fetal glucose uptake rate was observed. Chronic hypoglycemia did not change GLUT-3 concentrations, although uterine, uteroplacental, and fetal net glucose uptake rates were decreased. Thus maternal hyperglycemia causes a time-dependent decline in the entire placental glucose transporter pool (GLUT-1 and GLUT-3). In contrast, maternal hypoglycemia decreases GLUT-1 but not GLUT-3, resulting in a relatively increased GLUT-3 contribution to the placental glucose transporter pool, which could maintain glucose delivery to the placenta relative to the fetus when maternal glucose is low.
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Division of Neonatology and Developmental Biology, Department of Pediatrics, University of Pittsburgh, Magee-Womens Research Institute, Pittsburgh, Pennsylvania 15213, USA.
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Ehrhardt
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Hay
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Devaskar
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D000818:Animals; D001786:Blood Glucose / Q000502:physiology; D005260:Female; D005312:Fetal Blood / Q000502:physiology; D051274:Glucose Transporter Type 3; D006706:Homeostasis; D006943:Hyperglycemia / Q000503:physiopathology*; D007003:Hypoglycemia / Q000503:physiopathology*; D008431:Maternal-Fetal Exchange; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D010920:Placenta / Q000502:physiology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000503:physiopathology*; D012756:Sheep
D001786:Blood Glucose; D051274:Glucose Transporter Type 3; D009004:Monosaccharide Transport Proteins; D009419:Nerve Tissue Proteins