Relaxation of the mouse isolated aorta and carotid artery in response to adenosine analogues in genetically-modified mice lacking the adenosine A2A receptor.

Autor: Prentice, D. J., Kelly, M. D. W., Ledent, C., Hourani, S. M. O.
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Zdroj: Naunyn-Schmiedeberg's Archives of Pharmacology; Aug2002, Vol. 366 Issue 2, p127-133, 7p
Abstrakt: The aim of this study was to characterise the receptor(s) mediating responses to adenosine and/or adenosine analogues in mouse isolated aorta and carotid artery. In addition, since mice lacking the A2A adenosine receptor are reported to be hypertensive, the possibility that this gene deletion or the altered phenotype results in alteration of responses mediated via adenosine analogues was investigated. This was achieved by comparing results obtained in parallel within single experiments using tissues from A2A knock-out animals and their wild-type littermates. In aortic rings, adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) caused relaxations above 10 µM and 30 µM, respectively, which were unaffected by either 8-sulphophenyltheophylline (8-SPT, 100 µM) or A2A receptor knockout. 2-[p-(2-Carbonylethyl)phenylethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680) was virtually inactive. R-N6-Phenylisopropyladenosine (R-PIA) induced relaxations which were not inhibited by 8-SPT (100 µM) or altered by A2A receptor knockout. No A1-mediated contractile responses were observed in wild-type or knock-out tissues in contrast with results in mice of the same strain obtained commercially rather than from our breeding programme. In carotid artery rings NECA contracted at low concentrations (0.1–1 µM) and relaxed at higher concentrations. Curves to NECA were not different in tissues from wild-type and A2A receptor knock-out mice and both the contractile and relaxant phases were right-shifted by 8-SPT (100 µM) in tissues from animals of both genotype. 1,3-Dipropyl-8-cyclopentylxanthine (DPCPX, 3 nM) attenuated contractile NECA responses but did not affect relaxant responses. CGS 21680 was inactive in carotid artery rings from both wild-type and A2A receptor knock-out mice. In the presence of DPCPX (30 nM) to abolish contractions, R-PIA induced relaxant curves which were not different in tissues from wild-type and A2A knock-out mice and were not inhibited by 8-SPT (100 µM). These results confirm the absence of A2A or A2B receptors in murine aorta and suggest that relaxations to NECA in carotid artery are A2B receptor-mediated whilst contractions are A1 receptor-mediated. They also indicate the presence of an antagonist-resistant site activated by R-PIA in both vascular preparations. There is no evidence for compensatory changes in responses mediated by adenosine and its analogues due to the gene deletion or the reported resulting hypertensive phenotype in either aortic or carotid arterial rings obtained from A2A knock-out mice. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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