Inhibition of Nitrobenzylthioinosine-Sensitive Adenosine Transport by Elevated d -Glucose Involves Activation of P 2Y2 Purinoceptors in Human Umbilical Vein Endothelial Cells
2002; Lippincott Williams & Wilkins; Volume: 90; Issue: 5 Linguagem: Inglês
10.1161/01.res.0000012582.11979.8b
ISSN1524-4571
AutoresJorge Parodí, Carlos A. Flores, Claudio Aguayo, M.I. Rudolph, Paola Casanello, Luis Sobrevía,
Tópico(s)Lanthanide and Transition Metal Complexes
ResumoChronic 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 μmol/L ATP, ATP-γ-S, or UTP, but not ADP or α,β-methylene ATP, reduced adenosine transport with no change in transport affinity. Inhibition of transport by d -glucose, ATP, and ATP-γ-S was associated with reduced maximal binding, with no changes in the apparent dissociation constant for nitrobenzylthioinosine (NBMPR). A significant reduction (≈60±10%, P <0.05; n=6) in the number of human equilibrative NBMPR-sensitive nucleoside transporters (hENT1s) per cell (1.8±0.1×10 6 in 5 mmol/L d -glucose) and in hENT1 mRNA levels was observed in cells exposed to d -glucose or ATP-γ-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 P 2Y purinoceptor antagonist), suramin (Gα s protein inhibitor), or hexokinase but not by pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid (nonselective P 2 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 P 2Y2 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.
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