title: Inhibition of nitrobenzylthioinosine-sensitive adenosine transport by elevated D-glucose involves activation of P2Y2 purinoceptors in human umbilical vein endothelial cells.
abstract: Chronic incubation with elevated D-glucose reduces adenosine transport in endothelial cells. In this study, exposure of human umbilical vein endothelial cells to 25 mmol/L D-glucose or 100 micromol/L ATP, ATP-gamma-S, or UTP, but not ADP or alpha,beta-methylene ATP, reduced adenosine transport with no change in transport affinity. Inhibition of transport by D-glucose, ATP, and ATP-gamma-S was associated with reduced maximal binding, with no changes in the apparent dissociation constant for nitrobenzylthioinosine (NBMPR). A significant reduction (approximately 60+/-10%, P<0.05; n=6) in the number of human equilibrative NBMPR-sensitive nucleoside transporters (hENT1s) per cell (1.8+/-0.1x10(6) in 5 mmol/L D-glucose) and in hENT1 mRNA levels was observed in cells exposed to D-glucose or ATP-gamma-S. Incubation with elevated D-glucose, but not with D-mannitol, increased the ATP release by 3+/-0.2-fold. The effects of D-glucose and nucleotides on the number and activity of hENT1 and hENT1 mRNA were blocked by reactive blue 2 (nonspecific P2Y purinoceptor antagonist), suramin (Galpha(s) protein inhibitor), or hexokinase but not by pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (nonselective P2 purinoceptor antagonist). Our findings demonstrate that inhibition of adenosine transport via hENT1 in endothelial cells cultured in 25 mmol/L D-glucose could be due to stimulation of P2Y2 purinoceptors by ATP, which is released from these cells in response to D-glucose. This could be a mechanism to explain in part the vasodilatation observed in the early stages of diabetes mellitus or in response to D-glucose infusion.
authors.affiliation: Cellular and Molecular Physiology Laboratory, Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile.
authors.forename: Jorge
authors.initials: J
authors.lastname: Parodi
authors.forename: Carlos
authors.initials: C
authors.lastname: Flores
authors.forename: Claudio
authors.initials: C
authors.lastname: Aguayo
authors.forename: M Isolde
authors.initials: MI
authors.lastname: Rudolph
authors.forename: Paola
authors.initials: P
authors.lastname: Casanello
authors.forename: Luis
authors.initials: L
authors.lastname: Sobrevia
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D033721:Equilibrative Nucleoside Transporter 1; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058473:Receptors, Purinergic P2Y2; D013868:Thioinosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D014471:Umbilical Veins; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D033721:Equilibrative Nucleoside Transporter 1; D026901:Membrane Transport Proteins; C546385:P2RY2 protein, human; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; C438649:SLC29A1 protein, human; C022571:adenosine 5'-O-(3-thiotriphosphate); D013868:Thioinosine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C001789:4-nitrobenzylthioinosine; D005947:Glucose; D000241:Adenosine; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D014544:Uridine Triphosphate