3.5 The vascular effects of BK-(1-9) fragments are not mediated
by the activation of the kinin receptors
To assess the relevance of kinin receptors in the vasorelaxation of
aortic ring preparations induced by BK-(1-9) fragments, we used
pharmacological antagonists of either B1 and
B2 receptors, respectively
Lys-(des-Arg9-Leu8)-BK-(1-9) (100
nM) and HOE-140 (100 nM). The vasorelaxant effect induced by BK-(1-9)
was abolished by antagonism of either B2 receptors
(Figure 6A) or B1 receptors (Figure 6D). Interestingly,
vasorelaxation induced by BK-(1-7) (Figures 6B and E) and BK-(1-5)
(Figures 6C and F) were not altered in the presence of either antagonist
of the kinin receptors.
The expression of mRNA for the kinin receptors was also assessed in rat
thoracic aorta by qPCR. The mRNA for both B1 and
B2 receptors were detected in the rat thoracic aorta,
but the expression of B2 receptor mRNA was significantly
higher than that of B1 receptor mRNA (Figure 6G). Taken
together, the results indicate that the vasorelaxation of rat aortic
rings induced by BK-(1-7) and BK-(1-5) was independent of the activation
of B1 receptor and/or B2 receptors.