that mRNA for rat elastase-2 was detected in the rat carotid
arteries makes this isolated vascular preparation suitable to
investigate the expression and function of this non-ACE
pathway for Ang II generation in different rat pathophysiological
conditions. In rat carotid artery, contractile responses elicited
by Ang II and related peptides were highly reproducible,
completely blocked by the AT
1
-receptor antagonist losartan,
and not affected by PD123319, a selective AT
2
-receptor
antagonist. These data indicate that AT
1
receptor-mediated
vasoconstriction is not opposed by activation of AT
2
-receptor
in the rat carotid artery, as was demonstrated in the rat isolated
uterine artery.
29
The same approach failed to reveal an important
functional role for elastase-2 in the rat aorta. In this artery
ACE seems to be the predominant pathway for Ang II
production from Ang I. In addition, the less intense expression
of elastase-2 mRNA in aortic tissue compared with carotid and
mesenteric tissues seems to corroborate this interpretation and
give an explanation for the lack of effect of PDA in aortic
rings.
CONCLUSION
In this study we demonstrated that mRNA for elastase-2
could be detected in the rat carotid artery tissue, and we also
provided pharmacological evidence that rat elastase-2 has an
important functional alternative pathway to ACE in Ang II
generation in this vascular tissue but not in aortic tissue.
ACKNOWLEDGMENT
The authors are grateful to Osmar Vettore for excellent
technical assistance.
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Volume 46, Number 4, October 2005