Functional expression of kinin B1 and B2 receptors in mouse abdominal aorta

ABSTRACT

Previous studies have shown that the vascular reactivity of the mouse aorta differs substantially from that of the rat aorta in response to several agonists such as angiotensin II, endothelin-1 and isoproterenol. However, no information is available about the agonists bradykinin (BK) and DesArg9BK (DBK). Our aim was to determine the potential expression of kinin B1 and B2 receptors in the abdominal mouse aorta isolated from C57BL/6 mice. Contraction and relaxation responses to BK and DBK were investigated using isometric recordings. The kinins were unable to induce relaxation but concentration-contraction response curves were obtained by applying increasing concentrations of the agonists BK and DBK. These effects were blocked by the antagonists Icatibant and R-715, respectively. The potency (pD2) calculated from the curves was 7.0 ± 0.1 for BK and 7.3 ± 0.2 for DBK. The efficacy was 51 ± 2 percent for BK and 30 ± 1 percent for DBK when compared to 1 æM norepinephrine. The concentration-dependent responses of BK and DBK were markedly inhibited by the arachidonic acid inhibitor indomethacin (1 æM), suggesting a mediation by the cyclooxygenase pathway. These contractile responses were not potentiated in the presence of the NOS inhibitor L-NAME (1 mM) or endothelium-denuded aorta, indicating that the NO pathway is not involved. We conclude that the mouse aorta constitutively contains B1 and B2 subtypes of kinin receptors and that stimulation with BK and DBK induces contractile effect mediated by endothelium-independent vasoconstrictor prostanoids.