Relaxation of mouse isolated aorta to adenosine and its analogues does not involve adenosine A(1), A(2) or A(3) receptors.

Relaxations to adenosine and analogues were investigated in the mouse aorta in the presence of the adenosine A(1) receptor-selective antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 30 nM), which did not affect relaxations to adenosine or its analogue N(6)-R-phenylisopropyladenosine (R-PIA) but abolished contractile adenosine A(1) receptor-mediated responses to these agonists. Relaxations to adenosine, 5'-N-ethylcarboxamidoadenosine, R-PIA, 2-[p-(2-carbonylethyl)-phenylethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680), and N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) were unaffected by the adenosine A(1)/A(2) receptor antagonist 8-sulphophenyltheophylline (100 microM). IB-MECA relaxations were unaffected by the adenosine A(3) receptor-selective antagonist 3-ethyl-5-benzyl-2-methyl-6-phenyl-4-phenylethynyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS1191, 30 microM) and R-PIA relaxations were unaffected by N(G)-nitro-L-arginine methyl ester (100 microM) and endothelium removal. In conclusion, relaxant responses to adenosine and analogues do not involve adenosine A(1), A(2) or A(3) receptors and are endothelium- and nitric oxide-independent.