Presence of functional angiotensin II receptor and angiotensin converting enzyme in the aorta of the snake Bothrops jararaca

AimAngiotensin II (Ang II) interacts with AT1 and AT2 receptors and, in some vertebrates, with an Ang II binding site showing low affinity for AT1 and AT2 receptor antagonists. This study was carried out to characterize the Ang II receptor, and the presence of an angiotensin-converting enzyme (ACE) in the aorta of the Bothrops jararaca snake.Main methodContraction induced by Ang I or II in aortic ring from the snake was evaluated in the absence or in the presence of ACE-blocker or Ang II antagonists.Key findingsAng II analogs, modified at positions 1 and 5, induced vasoconstriction with differences in their potencies. The relative rank order was: [Asp1, Val5] Ang II = [Asp1, Ile5] Ang II ⋙ [Asn1, Val5] Ang II. ACE-like activity was detected, as well as an Ang II receptor with low affinity for AT1 and AT2 selective receptor antagonists (pKB values of 5.62 ± 0.23 and 5.08 ± 0.25). A disulfide reducing agent almost abolished the Ang II effect, while an alpha adrenoceptor antagonist, or removing the endothelium, did not modify the Ang II effect. These results indicate that the B. jararaca aorta has an Ang II receptor pharmacologically distinct from AT1 and AT2 receptors, and the vasoconstrictor effect observed is independent of catecholamine or endothelium modulation. ACE and the AT receptor in the aorta of B. jararaca may be part of a tissue renin-angiotensin system.SignificanceThe data contribute to the knowledge of the renin-angiotensin system in vertebrate species, and provide insight into the understanding of snake Ang II receptor characteristics and diversity.