title: Mechanisms underlying reduced P2Y(1) -receptor-mediated relaxation in superior mesenteric arteries from long-term streptozotocin-induced diabetic rats.
abstract: OBJECTIVE
  Extracellular nucleotides activate cell-surface purinergic (P2) receptors, contribute to the local regulation of vascular tone and play important roles in pathophysiological states. However, little is known about the vasodilator effects of P2Y(1) -receptor activation in diabetic states. We hypothesized that in a model of established type 1 diabetes, long-term streptozotocin (STZ)-induced diabetic rats, the arterial relaxation elicited by a P2Y(1) -receptor agonist would be impaired.
  
  
  METHODS
  Relaxations to adenosine 5'-diphosphate sodium salt (ADP), 2-MeSADP (selective P2Y(1) -receptor agonist) and adenosine 5'-triphosphate disodium salt (ATP) were examined in superior mesenteric artery rings from long-term STZ-induced diabetic rats (at 50-57 weeks after STZ injection). ADP-stimulated nitric oxide (NO) production in the superior mesenteric artery was assessed by measuring the levels of NO metabolites. Mesenteric artery expressions of P2Y(1) receptor, and ADP-stimulated levels of phosphorylated endothelial NO synthase (eNOS) (at Ser(1177) and at Thr(495) ) and eNOS were detected by Western blotting.
  
  
  RESULTS
  Arteries from diabetic rats exhibited (vs. those from age-matched control rats): (i) reduced ADP-induced relaxation, which was partly or completely inhibited by endothelial denudation, by NOS inhibitor treatment and by a selective P2Y(1) -receptor antagonist, (ii) reduced 2-MeSADP-induced relaxation, (iii) reduced ADP-stimulated release of NO metabolites and (iv) impaired ADP-induced stimulation of eNOS activity (as evidenced by reduced the fold increase in eNOS phosphorylation at Ser(1177) with no difference in fold increase in eNOS phosphorylation at Thr(495) ). The protein expression of P2Y(1) receptor did not differ between diabetic and control arteries.
  
  
  CONCLUSIONS
  These results suggest that P2Y(1) -receptor-mediated vasodilatation is impaired in superior mesenteric arteries from long-term type 1 diabetic rats. This impairment is because of reduced P2Y(1) -receptor-mediated NO signalling, rather than to reduced P2Y(1) -receptor expression.
authors: Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan.
authors: K
authors: K
authors: Ishida
authors: T
authors: T
authors: Matsumoto
authors: K
authors: K
authors: Taguchi
authors: K
authors: K
authors: Kamata
authors: T
authors: T
authors: Kobayashi
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000502:physiology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000503:physiopathology*; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism / Q000503:physiopathology*; D003925:Diabetic Angiopathies / Q000378:metabolism / Q000503:physiopathology*; D004195:Disease Models, Animal; D008297:Male; D017538:Mesenteric Artery, Superior / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism; D058912:Purinergic P2Y Receptor Agonists / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D058472:Receptors, Purinergic P2Y1 / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology; D013995:Time; D014664:Vasodilation / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D058912:Purinergic P2Y Receptor Agonists; D058472:Receptors, Purinergic P2Y1; D013873:Thionucleotides; D009569:Nitric Oxide; C002480:methylthio-ADP; D000244:Adenosine Diphosphate; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat