Modulation of A2A adenosine receptors and associated Galphas proteins by ZM 241385 treatment of porcine coronary artery.
Functional regulation and expression of the adenosine A2A receptor and associated G-protein were investigated in porcine coronary artery exposed to an A2A receptor antagonist, ZM 241385 (4-(2-[7-amino-2-(2-furyl)[1,2,4]-triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol). The arteries were incubated for 3 days in culture medium in the absence (control) and presence (treated) of 10 microM ZM 241385. Changes in isometric tension by adenosine receptor agonists were evaluated in endothelium-free tissues. ZM 241385-treatment produced a statistically significant rightward displacement of CGS-21680, NECA, and CAD concentration-response curves compared with the respective controls (P < 0.05). The EC50, expressed in nM, values in treated and control tissues were: 617.3 +/- 23 versus 24.9 +/- 1.5 for CGS-21680 (2-(p-(2-carboxyethyl)phenethylamino)-5'N-ethylcarboxamidoadenosine), 27.4 +/- 6.3 versus 3.06 +/- 0.8 for NECA (5'-N-ethylcarboxamidoadenosine), and 5786.2 +/- 160 versus 89.2 +/- 24.1 for CAD (chloroadenosine). However, the relaxing effect of forskolin remained unchanged in treated and control tissues. The concentration-response curves for NECA, CAD, and CGS-21680 were also displaced to the right when cAMP levels were measured in treated and control smooth muscle cells while no differences were observed with forskolin. Quantitative Western blot analysis demonstrated that the density of A2A receptors increased in ZM 241385-treated artery. We also showed a significant decrease in Galphas protein levels after ZM 241385 treatment compared with control. Taken together, these data indicate that prolonged blockade of A2A receptors in the coronary artery leads to desensitization of the functional effects of adenosine agonists by a mechanism that involves decreases in cAMP production. This was associated with an up-regulation of A2A receptors and a decrease in Galphas protein expression.
Rekik
Moez
M
Department of Pharmacology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
Mustafa
Jamal S
JS
D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D013552:Swine; D014227:Triazines / Q000494:pharmacology*; D014230:Triazoles / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D014227:Triazines; D014230:Triazoles; C097270:ZM 241385; D000242:Cyclic AMP