Article date: September 2002
By: Yohann Rautureau, Gilles Toumaniantz, Sabrina Serpillon, Philippe Jourdon, Jean‐Noël Trochu, Chantal Gauthier in Volume 137, Issue 2, pages 153-161
We have previously demonstrated that β3‐adrenoceptor (β3‐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 β3‐AR to confirm our functional study and to complete the signalling pathway of β3‐AR in rat aorta.
By RT–PCR, we have detected β3‐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 β3‐AR from adipocytes. The localization of β3‐AR in aortic endothelial cells was confirmed by immunohistochemistry using a rat β3‐AR antibody.
To identify the G protein linked to β3‐AR, experiments were performed in rat pre‐treated with PTX (10 μg kg−1), a Gi/0 protein inhibitor. The blockage of Gi/0 protein by PTX was confirmed by the reduction of vasorelaxation induced by UK 14304, a selective α2‐AR agonist. The cumulative concentration‐response curve for SR 58611A, a β3‐AR agonist, was not significantly modified on aorta rings from PTX pre‐treated rats.
At the same level of contraction, the relaxations induced by 10 μM SR 58611A were significantly reduced in 30 mM‐KCl pre‐constricted rings (Emax=16.7±8.4%, n=5), in comparison to phenylephrine (0.3 μM) pre‐constricted rings (Emax=49.11±11.0%, n=5, P<0.05). In addition, iberotoxin (0.1 μM), glibenclamide (1 μM) and 4‐aminopyridine (1 mM), selective potassium channels blockers of KCa, KATP, and Kv respectively, decreased the SR 58611A‐mediated relaxation.
We conclude that β3‐AR is preferentially expressed in rat aortic endothelial cells. β3‐AR‐mediated aortic relaxation is independent of Gi/0 proteins stimulation, but results from the activation of several potassium channels, KCa, KATP, and Kv.
We have previously demonstrated that β3‐adrenoceptor (β3‐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 β3‐AR to confirm our functional study and to complete the signalling pathway of β3‐AR in rat aorta.
By RT–PCR, we have detected β3‐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 β3‐AR from adipocytes. The localization of β3‐AR in aortic endothelial cells was confirmed by immunohistochemistry using a rat β3‐AR antibody.
To identify the G protein linked to β3‐AR, experiments were performed in rat pre‐treated with PTX (10 μg kg−1), a Gi/0 protein inhibitor. The blockage of Gi/0 protein by PTX was confirmed by the reduction of vasorelaxation induced by UK 14304, a selective α2‐AR agonist. The cumulative concentration‐response curve for SR 58611A, a β3‐AR agonist, was not significantly modified on aorta rings from PTX pre‐treated rats.
At the same level of contraction, the relaxations induced by 10 μM SR 58611A were significantly reduced in 30 mM‐KCl pre‐constricted rings (Emax=16.7±8.4%, n=5), in comparison to phenylephrine (0.3 μM) pre‐constricted rings (Emax=49.11±11.0%, n=5, P<0.05). In addition, iberotoxin (0.1 μM), glibenclamide (1 μM) and 4‐aminopyridine (1 mM), selective potassium channels blockers of KCa, KATP, and Kv respectively, decreased the SR 58611A‐mediated relaxation.
We conclude that β3‐AR is preferentially expressed in rat aortic endothelial cells. β3‐AR‐mediated aortic relaxation is independent of Gi/0 proteins stimulation, but results from the activation of several potassium channels, KCa, KATP, and Kv.
British Journal of Pharmacology (2002) 137, 153–161. doi:10.1038/sj.bjp.0704867
DOI: 10.1038/sj.bjp.0704867
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