Attenuated Aortic Vasodilation and Sympathetic Prejunctional Facilitation in Epinephrine-Deficient Mice: Selective Impairment of beta(2)-Adrenoceptor Responses

作者：Moreira Rodrigues Monica^*; Graca Ana L; Ferreira Marlene; Afonso Joana; Serrao Paula; Morato Manuela; Ferreirinha Fatima; Correia de Sa Paulo; Ebert Steven N; Moura Daniel

来源：Journal of Pharmacology and Experimental Therapeutics, 2014, 351(2): 243-249.

DOI：10.1124/jpet.114.217281

It has been suggested that there is a link between epinephrine synthesis and the development of beta(2)-adrenoceptor-mediated effects, but it remains to be determined whether this development is triggered by epinephrine. The aim of this study was to characterize beta-adrenoceptor-mediated relaxation and facilitation of norepinephrine release in the aorta of phenylethanolamine-N-methyltransferase-knockout (Pnmt-KO) mice. Catecholamines were quantified by reverse-phase high-performance liquid chromatography-electrochemical detection. Aortic rings were mounted in a myograph to determine concentration-response curves to selective beta(1)- or beta(2)-adrenoceptor agonists in the absence or presence of selective beta(1)- or beta(2)-adrenoceptor antagonists. Aortic rings were also preincubated with [H-3] norepinephrine to measure tritium overflow elicited by electrical stimulation in the presence of increasing concentrations of nonselective beta- or selective beta(2)-adrenoceptor agonists. beta(2)-Adrenoceptor protein density was evaluated by Western blotting and beta(2)-adrenoceptor localization by immunohistochemistry. Epinephrine is absent in Pnmt-KO mice. The potency and the maximal effect of the beta(2)-adrenoceptor agonist terbutaline were lower in Pnmt-KO than in wild-type (WT) mice. The selective beta(2)-adrenoceptor antagonist ICI 118,551 [(+/-)-erythro-(S*, S*)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl) amino]-2-butanol hydrochloride] antagonized the relaxation caused by terbutaline in WT but not in Pnmt-KO mice. Isoproterenol and terbutaline induced concentration-dependent increases in tritium overflow in WT mice only. beta(2)-Adrenoceptor protein density was decreased in membrane aorta homogenates of Pnmt-KO mice, and this finding was supported by immunofluorescence confocal microscopy. In conclusion, epinephrine is crucial for beta(2)-adrenoceptor-mediated vasodilation and facilitation of norepinephrine release. In the absence of epinephrine, beta(2)-adrenoceptor protein density was decreased in aorta cell membranes, thus potentially hindering its functional activity.

• 出版日期2014-11