Direct demonstration of beta1- and evidence against beta2- and beta3-adrenoceptors, in smooth muscle cells of rat small mesenteric arteries.
1 Recent evidence supports additional subtypes of vasodilator beta-adrenoceptor (beta-AR) besides the 'classical' beta(2). The aim of this study was to investigate the distribution of beta-ARs in the wall of rat mesenteric resistance artery (MRA), to establish the relative roles of beta-ARs in smooth muscle and other cell types in mediating vasodilatation and to analyse this in relation to the functional pharmacology. 2 We first examined the vasodilator beta-AR subtype using 'subtype-selective' agonists against the, commonly employed, phenylephrine-induced tone. Concentration-related relaxation was produced by isoprenaline (pEC(50): 7.70+/-0.1) (beta(1) and beta(2)). Salbutamol (beta(2)), BRL 37344 (beta(3)) and CGP 12177 (atypical beta) caused relaxation but were 144, 100 and 263 times less potent than isoprenaline; the 'beta(3)-adrenoceptor agonist' CL 316243 was ineffective. 3 In arteries precontracted with 5-HT or U 46619, isoprenaline produced concentration-related relaxation but salbutamol, BRL 37344, CGP 12177 and CL 316243 did not. SR 59230A, CGP 12177 and BRL 37344 caused a parallel rightward shift in the concentration-response curve to phenylephrine indicating competitive alpha(1)-AR antagonism, explaining the false-positive 'vasodilator' action against phenylephrine-induced tone. Endothelial denudation but not L-NAME slightly attenuated isoprenaline-mediated vasodilatation in phenylephrine and U 46619 precontracted MRA. 4 The beta-AR fluorescent ligand BODIPY TMR-CGP 12177 behaved as an irreversible beta(1)-AR antagonist in MRA and bound to the surface and inside vascular smooth muscle cells in intact vascular wall. Beta-ARs in smooth muscle cells were observed in a perinuclear location, consistent with the location of Golgi and endoplasmic reticulum. 5 Binding of BODIPY TMR-CGP 12177 was inhibited by BAAM (1 microM) in all three vascular tunics, confirming the presence of beta-ARs in adventitia, media and intima. Binding in adventitia was observed in both neuronal and non-neuronal cell types. Lack of co-localisation with a fluorescent ligand for alpha-ARs confirms the selectivity of BODIPY TMR-CGP 12177 for beta-ARs over alpha-ARs. 6 Our results support the presence of functional vasodilator beta(1)-ARs and show that they are mainly located in smooth muscle cells. Furthermore, we have demonstrated, for the first time, the usefulness of BODIPY TMR-CGP 12177 for identifying beta-AR distribution in the 'living' vascular wall.
Briones
Ana M
AM
Departament de Farmacologia, de Terapeutica i de Toxicologia, Institut de Neurociències, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellatera, Spain.
Daly
Craig J
CJ
Jimenez-Altayo
Francesc
F
Martinez-Revelles
Sonia
S
Gonzalez
Jose M
JM
McGrath
John C
JC
Vila
Elisabet
E
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002478:Cells, Cultured; D004149:Dioxoles / Q000494:pharmacology; D004983:Ethanolamines / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008638:Mesenteric Arteries / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D011943:Receptors, Adrenergic, beta / Q000378:metabolism* / Q000502:physiology; D014664:Vasodilation / Q000502:physiology
C097869:3-(2-ethylphenoxy)-1-(1,2,3,4-tetrahydronaphth-1-ylamino)-2-propanol oxalate; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D001896:Boron Compounds; D004149:Dioxoles; D004983:Ethanolamines; D007093:Imidazoles; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C076126:disodium (R,R)-5-(2-((2-(3-chlorophenyl)-2-hydroxyethyl)-amino)propyl)-1,3-benzodioxole-2,3-dicarboxylate; C088725:BODIPY-CGP 12177; D010656:Phenylephrine; C057368:BRL 37344