title: Impairment of acetylcholine-mediated endothelium-dependent relaxation in isolated parotid artery of the alloxan-induced diabetic rabbit.
abstract: The aim of this study was to assess the effect of type 1 diabetes mellitus (induced by a single intravenous injection of 100 mg kg(-1) of alloxan) on acetylcholine (ACh)-induced relaxation in isolated rabbit parotid gland feeding artery. Isometric force measurements and quantification of inducible nitric oxide synthase (iNOS) mRNA by real-time RT-PCR were made in parotid artery rings from diabetic and control rabbits. Acetylcholine induced concentration- and endothelium-dependent vasorelaxation that was significantly decreased in parotid artery rings from diabetic rabbits. Schild analysis of the ACh vasorelaxant effect, in the presence of selective muscarinic receptor antagonists, revealed involvement of the M(3) receptor subtype in parotid artery rings from both control and diabetic rabbits, with no change in antagonist affinity constants. The inhibitory effects of indomethacin, a non-selective inhibitor of cyclooxygenase, and of high potassium, an inhibitor of hyperpolarization, on ACh vasorelaxation were increased. The effect of N(G) -nitro-l-arginine, a non-selective inhibitor of NOS, was decreased in diabetes. S-methylisothiourea, a selective inhibitor of iNOS, significantly reduced ACh vasorelaxation only in parotid artery rings from diabetic rabbits. Also, up-regulation of iNOS mRNA expression was detected in parotid artery rings from diabetic rabbits. These results suggest that in parotid artery rings from diabetic rabbits, impaired endothelium-dependent vasorelaxation to ACh appears to be caused by the loss of a nitric oxide-mediated component and increased iNOS expression, and is unlikely to be caused by a change at the M(3) receptor level.
authors: Department of Pharmacology, University of Belgrade, Serbia.
authors: Jelena
authors: J
authors: Roganović
authors: Miroslav
authors: M
authors: Radenković
authors: Nikola
authors: N
authors: Tanić
authors: Nasta
authors: N
authors: Tanić
authors: Nina
authors: N
authors: Petrović
authors: Dragica
authors: D
authors: Stojić
mesh_terms: D000109:Acetylcholine / Q000037:antagonists & inhibitors*; D000496:Alloxan; D000818:Animals; D001158:Arteries / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D003922:Diabetes Mellitus, Type 1 / Q000139:chemically induced / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects; D007550:Isothiuronium / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II / Q000032:analysis / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010306:Parotid Gland / Q000098:blood supply*; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D011897:Random Allocation; D043587:Receptor, Muscarinic M3 / Q000037:antagonists & inhibitors; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D018727:Muscarinic Antagonists; D043587:Receptor, Muscarinic M3; D014662:Vasoconstrictor Agents; D009599:Nitroprusside; D010656:Phenylephrine; D019335:Nitroarginine; D007550:Isothiuronium; D000496:Alloxan; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C027744:S-methylisothiopseudouronium; D000109:Acetylcholine; D011188:Potassium; D001920:Bradykinin; D007213:Indomethacin