par Sharifi-Sanjani, Maryam;Zhou, Xueping;Asano, Shinichi;Tilley, Stephen S.L.;Ledent, Catherine ;Teng, Bunyen;Dick, Gregory G.M.;Mustafa, Jamal S.J.
Référence American journal of physiology. Heart and circulatory physiology, 304, 10, page (H1294-H1301)
Publication Publié, 2013
Article révisé par les pairs
Résumé : Myocardial metabolites such as adenosine mediate reactive hyperemia, in part, by activating ATP-dependent K+ (KATP) channels in coronary smooth muscle. In this study, we investigated the role of adenosine A2A and A2B receptors and their signaling mechanisms in reactive hyperemia. We hypothesized that coronary reactive hyperemia involves A2A receptors, hydrogen peroxide (H2O2), and KATP channels. We used A2A and A2B knockout (KO) and A2A/2B double KO (DKO) mouse hearts for Langendorff experiments. Flow debt for a 15-s occlusion was repaid 128 ± 8% in hearts from wild-type (WT) mice; this was reduced in hearts from A2A KO and A2A/2B DKO mice (98 ± 9 and 105 ± 6%; P < 0.05), but not A2B KO mice (123 ± 13%). Patch-clamp experiments demonstrated that adenosine activated glibenclamide-sensitive KATP current in smooth muscle cells from WT and A2B KO mice (90 ± 23% of WT) but not A2A KO or A2A/A2B DKO mice (30 ± 4 and 35 ± 8% of WT; P < 0.05). Additionally, H2O2 activated KATP current in smooth muscle cells (358 ± 99%; P < 0.05). Catalase, an enzyme that breaks down H2O2, attenuated adenosine-induced coronary vasodilation, reducing the percent increase in flow from 284 ± 53 to 89 ± 13% (P < 0.05). Catalase reduced the repayment of flow debt in hearts from WT mice (84 ± 9%; P < 0.05) but had no effect on the already diminished repayment in hearts from A2A KO mice (98 ± 7%). Our findings suggest that adenosine A2A receptors are coupled to smooth muscle KATP channels in reactive hyperemia via the production of H2O2 as a signaling intermediate. © 2013 the American Physiological Society.

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