RT Journal Article
SR Electronic
T1 Attenuated Aortic Vasodilation and Sympathetic Prejunctional Facilitation in Epinephrine-Deficient Mice: Selective Impairment of <em>β</em><sub>2</sub>-Adrenoceptor Responses
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 243
OP 249
DO 10.1124/jpet.114.217281
VO 351
IS 2
A1 Mónica Moreira-Rodrigues
A1 Ana L. Graça
A1 Marlene Ferreira
A1 Joana Afonso
A1 Paula Serrão
A1 Manuela Morato
A1 Fátima Ferreirinha
A1 Paulo Correia-de-Sá
A1 Steven N. Ebert
A1 Daniel Moura
YR 2014
UL http://jpet.aspetjournals.org/content/351/2/243.abstract
AB 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 [3H]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.