Attenuated aortic vasodilation and sympathetic prejunctional facilitation in epinephrine-deficient mice: selective impairment of β2-adrenoceptor responses.

نویسندگان

  • Mónica Moreira-Rodrigues
  • Ana L Graça
  • Marlene Ferreira
  • Joana Afonso
  • Paula Serrão
  • Manuela Morato
  • Fátima Ferreirinha
  • Paulo Correia-de-Sá
  • Steven N Ebert
  • Daniel Moura
چکیده

It has been suggested that there is a link between epinephrine synthesis and the development of β2-adrenoceptor-mediated effects, but it remains to be determined whether this development is triggered by epinephrine. The aim of this study was to characterize β-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 β1- or β2-adrenoceptor agonists in the absence or presence of selective β1- or β2-adrenoceptor antagonists. Aortic rings were also preincubated with [(3)H]norepinephrine to measure tritium overflow elicited by electrical stimulation in the presence of increasing concentrations of nonselective β- or selective β2-adrenoceptor agonists. β2-Adrenoceptor protein density was evaluated by Western blotting and β2-adrenoceptor localization by immunohistochemistry. Epinephrine is absent in Pnmt-KO mice. The potency and the maximal effect of the β2-adrenoceptor agonist terbutaline were lower in Pnmt-KO than in wild-type (WT) mice. The selective β2-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. β2-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 β2-adrenoceptor-mediated vasodilation and facilitation of norepinephrine release. In the absence of epinephrine, β2-adrenoceptor protein density was decreased in aorta cell membranes, thus potentially hindering its functional activity.

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Attenuated Aortic Vasodilation and Sympathetic Prejunctional Facilitation in Epinephrine-Deficient Mice: Selective Impairment of b2-Adrenoceptor Responses

It has been suggested that there is a link between epinephrine synthesis and the development of b2-adrenoceptor–mediated effects, but it remains to be determined whether this development is triggered by epinephrine. The aim of this study was to characterize b-adrenoceptor–mediated relaxation and facilitation of norepinephrine release in the aorta of phenylethanolamine-Nmethyltransferase–knockou...

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عنوان ژورنال:
  • The Journal of pharmacology and experimental therapeutics

دوره 351 2  شماره 

صفحات  -

تاریخ انتشار 2014