title: Mechanism of adenosine-induced vasodilation in rat diaphragm microcirculation.
abstract: The mechanism of adenosine-induced vasodilation in rat diaphragm microcirculation was investigated using laser Doppler flowmetry. Adenosine (10(-5), 3.2 x 10(-5), and 10(-4) M), the nonselective adenosine agonist 5'-N-ethylcarboxamido-adenosine (NECA) (10(-8)-10(-7) M), the specific A(2A) agonist 2-p-(2-carboxyethyl)phenyl-amino-5'-N-ethyl carboxamidoadenosine (CGS-21680) (10(-8)-10(-7) M), and the adenosine agonist with higher A(1)-receptor affinity, R-N(6)-phenylisopropyladenosine (R-PIA) (10(-7), 3.2 x 10(-7), and 10(-6) M) elicited a similar degree of incremental increase of microcirculatory flow in a dose-dependent manner. The ATP-dependent potassium (K(ATP)) channel blocker glibenclamide (3.2 x 10(-6) M) significantly attenuated the vasodilation effects of these agonists. Adenosine-induced vasodilation could be significantly attenuated by the nonselective adenosine antagonist 8-(p-sulfophenyl)-theophylline (3 x 10(-5) M) or the selective A(2A) antagonist 4-(2-[7-amino-2-(2-furyl)[1,2, 4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl) phenol (ZM-241385, 10(-6) M), but not by the selective A(1) antagonist 8-cyclopentyl-1, 3-dipropylxanthine (5 x 10(-8) M). Adenylate cyclase inhibitor N-(cis-2-phenyl-cyclopentyl) azacyclotridecan-2-imine-hydrochloride (MDL-12330A, 10(-5)M) effectively suppressed the vasodilator response of adenosine and forskolin. These results suggest that adenosine-induced vasodilation in rat diaphragm microcirculation is mediated through the stimulation of A(2A) receptors, which are coupled to adenylate cyclase activation and opening of the K(ATP) channel.
authors.affiliation: Department of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan 704, Taiwan, Republic of China.
authors.forename: C W
authors.initials: CW
authors.lastname: Chen
authors.forename: H Y
authors.initials: HY
authors.lastname: Chang
authors.forename: T R
authors.initials: TR
authors.lastname: Hsiue
mesh_terms: D000241:Adenosine / Q000378:metabolism* / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D003964:Diaphragm / Q000098:blood supply* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000494:pharmacology; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D014665:Vasodilator Agents; D005576:Colforsin; D019830:Adenosine-5'-(N-ethylcarboxamide); D000262:Adenylyl Cyclases; D000241:Adenosine; D005905:Glyburide