Beta 3-adrenoceptor in rat aorta: molecular and biochemical characterization and signalling pathway.
1. We have previously demonstrated that beta(3)-adrenoceptor (beta(3)-AR) stimulation induces endothelium-dependent vasorelaxation in rat aorta through the activation of an endothelial NO synthase associated with an increase in intracellular cGMP. The aim of the present study was to localise beta(3)-AR to confirm our functional study and to complete the signalling pathway of beta(3)-AR in rat aorta. 2. By RT-PCR, we have detected beta(3)-AR transcripts both in aorta and in freshly isolated endothelial cells. The absence of markers for adipsin or hormone-sensitive lipase in endothelial cells excluded the presence of beta(3)-AR from adipocytes. The localization of beta(3)-AR in aortic endothelial cells was confirmed by immunohistochemistry using a rat beta(3)-AR antibody. 3. To identify the G protein linked to beta(3)-AR, experiments were performed in rat pre-treated with PTX (10 microg kg(-1)), a G(i/0) protein inhibitor. The blockage of G(i/0) protein by PTX was confirmed by the reduction of vasorelaxation induced by UK 14304, a selective alpha(2)-AR agonist. The cumulative concentration-response curve for SR 58611A, a beta(3)-AR agonist, was not significantly modified on aorta rings from PTX pre-treated rats. 4. At the same level of contraction, the relaxations induced by 10 microM SR 58611A were significantly reduced in 30 mM-KCl pre-constricted rings (E(max)=16.7+/-8.4%, n=5), in comparison to phenylephrine (0.3 microM) pre-constricted rings (E(max)=49.11+/-11.0%, n=5, P<0.05). In addition, iberotoxin (0.1 microM), glibenclamide (1 microM) and 4-aminopyridine (1 mM), selective potassium channels blockers of K(Ca), K(ATP), and K(v) respectively, decreased the SR 58611A-mediated relaxation. 5. We conclude that beta(3)-AR is preferentially expressed in rat aortic endothelial cells. Beta(3)-AR-mediated aortic relaxation is independent of G(i/0) proteins stimulation, but results from the activation of several potassium channels, K(Ca), K(ATP), and K(v).
Laboratoire de Physiopathologie et de Pharmacologie Cellulaires et Moléculaires, INSERM U533, Hôtel-Dieu, Nantes, France.
Yohann
Y
Rautureau
Gilles
G
Toumaniantz
Sabrina
S
Serpillon
Philippe
P
Jourdon
Jean-Noël
JN
Trochu
Chantal
C
Gauthier
D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology*; D000068438:Brimonidine Tartrate; D004730:Endothelium, Vascular / Q000502:physiology; D019204:GTP-Binding Proteins / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D037342:Pertussis Toxin / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D011810:Quinoxalines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D022702:Receptors, Adrenergic, beta-3 / Q000235:genetics / Q000502:physiology*; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014664:Vasodilation
D015221:Potassium Channels; D011810:Quinoxalines; D012333:RNA, Messenger; D022702:Receptors, Adrenergic, beta-3; D013764:Tetrahydronaphthalenes; D000068438:Brimonidine Tartrate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; C076252:amibegron