[Vascular beta-adrenergic remodeling in rat transgenic model over-expressing endothelial beta3-adrenoceptors].
In rat thoracic aorta, the stimulation of endothelial beta3-adrenoceptors (beta-AR) produces a vasorelaxation through activation of a NO synthase pathway and an increase in cGMP levels. In hypertension, a global decrease of the beta-AR response has been described. In spontaneously hypertensive rats (SHR), we have shown that beta3-adrenoceptor-mediated relaxation was not modified in SHR aorta at the age of 12 weeks, in spite of an upregulation of beta3-adrenoceptors. In order to determine the consequences of an over-expression of the beta3-AR, we have developed a transgenic rat over-expressing specifically in endothelial cells the human beta3-AR (Tg beta3). By real-time quantitative PCR, we have determined the expression level of the different beta-AR subtypes. We confirmed an over-expression of the beta3-AR transcripts in Tg beta3 (ratio = 3.39 +/- 0.8; n=3 for Tg beta3 vs wild type [WT] animals). Surprisingly, we observed in Tg beta3 a decrease of beta1-AR transcripts (ratio = 0.76 +/- 0.03; n=3 for Tg beta3 vs WT animals) and no variation for beta2-AR transcripts (ratio = 1.95 +/- 0.60; n=3 for Tg beta3 vs WT animals). In aorta rings from WT and Tg beta3, the isoproterenol-induced relaxation was similar (WT: Emax = 82 +/- 6%, n=6; Tg beta3: Emax = 85 +/- 6, n=6). By contrast, in the presence of 10 microM nadolol, a beta1-, beta2-AR antagonist, the isoproterenol-induced response was significantly increased in Tg beta3 (WT: Emax = 68 +/- 6%, n=6: Tg beta3: Emax = 86 +/- 3; p < 0.01 vs WT). This effect was loss on denuded aortic rings. In conclusion, our study reported similar results to those obtained in hypertension in which a decrease of the beta-AR expression was associated to an elevation of the beta3-AR density. Moreover, this over-expression in our transgenic model is associated to a potential response induced by beta3-AR. Therefore, an activation of beta3-AR could supply the beta1- / beta2-AR decrease. Then, our transgenic model should be used to characterize the physiological consequences of this over-expression as well as to determine the putative involvement of this receptor in the pathogenesis of hypertension.
Toumaniantz
G
G
INSERM U533, l'Institut du thorax, Faculté de médecine, Nantes.
Seze
C
C
Serpillon
S
S
Menoret
S
S
Tesson
L
L
Anégone
I
I
Gauthier
C
C
D000818:Animals; D030801:Animals, Genetically Modified; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000502:physiology; D020869:Gene Expression Profiling; D006973:Hypertension / Q000503:physiopathology* / Q000662:veterinary; D008297:Male; D016133:Polymerase Chain Reaction; D051381:Rats; D017207:Rats, Sprague-Dawley; D022702:Receptors, Adrenergic, beta-3 / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*
D022702:Receptors, Adrenergic, beta-3