| 1. |
- Wang, Lingwei, et al.
(författare)
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ADP Acting on P2Y13 Receptors Is a Negative Feedback Pathway for ATP Release From Human Red Blood Cells.
- 2005
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Ingår i: Circulation Research. - 0009-7330. ; 96:Dec 16, s. 189-196
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Tidskriftsartikel (refereegranskat)abstract
- Red blood cells may regulate tissue circulation and O-2 delivery by releasing the vasodilator ATP in response to hypoxia. When released extracellularly, ATP is rapidly degraded to ADP in the circulation by ectonucleotidases. In this study, we show that ADP acting on P2Y(13) receptors on red blood cells serves as a negative feedback pathway for the inhibition of ATP release. mRNA of the ADP receptor P2Y(13) was highly expressed in human red blood cells and reticulocytes. The stable ADP analogue 2-MeSADP decreased ATP release from red blood cells by inhibition of cAMP. The P2Y(12) and P2Y(13) receptor antagonist AR-C67085 (30 mumol/L), but not the P2Y(1) blocker MRS2179, inhibited the effects of 2-MeSADP. At doses where AR-C67085 only blocks P2Y(12) (100 nmol/L), it had no effect. AR-C67085 and the nucleotidase apyrase increased cAMP per se, indicating a constant cAMP inhibitory effect of endogenous extracellular ADP. 2-MeSADP reduced plasma ATP concentrations in an in vivo pig model. Our results indicate that the ATP degradation product ADP inhibits ATP release by acting on the red blood cell P2Y(13) receptor. This negative feedback system could be important in the control of plasma ATP levels and tissue circulation.
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| 2. |
- Wihlborg, Anna-Karin, et al.
(författare)
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Positive inotropic effects by uridine triphosphate (UTP) and uridine diphosphate (UDP) via P2Y(2) and P2Y(6) receptors on cardiomyocytes and release of UTP in man during myocardial infarction
- 2006
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Ingår i: Circulation Research. - 0009-7330. ; 98:7, s. 970-976
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine a possible role for extracellular pyrimidines as inotropic factors for the heart. First, nucleotide plasma levels were measured to evaluate whether UTP is released in patients with coronary heart disease. Then, inotropic effects of pyrimidines were examined in isolated mouse cardiomyocytes. Finally, expression of pyrimidine-selective receptors ( a subgroup of the P2 receptors) was studied in human and mouse heart, using real time polymerase chain reaction, Western blot, and immunohistochemistry. Venous plasma levels of UTP were increased (57%) in patients with myocardial infarction. In electrically stimulated cardiomyocytes the stable P2Y(2/4) agonist UTP gamma S increased contraction by 52%, similar to beta(1)-adrenergic stimulation with isoproterenol (65%). The P2Y(6)-agonist UDP gamma S also increased cardiomyocyte contraction (35%), an effect abolished by the P2Y(6)-blocker MRS2578. The phospholipase C inhibitor U73122 inhibited both the UDP beta S and the UTP gamma S-induced inotropic effect, indicating an IP3-mediated effect via P2Y(6) receptors. The P2Y(14) agonist UDP-glucose was without effect. Quantification of mRNA with real time polymerase chain reaction revealed P2Y(2) as the most abundant pyrimidine receptor expressed in cardiomyocytes from man. Presence of P2Y(6) receptor mRNA was detected in both species and confirmed at protein level with Western blot and immunohistochemistry in man. In conclusion, UTP levels are increased in humans during myocardial infarction, giving the first evidence for UTP release in man. UTP is a cardiac inotropic factor most likely by activation of P2Y(2) receptors in man. For the first time we demonstrate inotropic effects of UDP, mediated by P2Y(6) receptors via an IP3-dependent pathway. Thus, the extracellular pyrimidines ( UTP and UDP) could be important inotropic factors involved in the development of cardiac disease.
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