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Abstract: Cardiovascular function is affected by many mechanisms, including the autonomic system, the kallikrein–kinin system (KKS), the renin–angiotensin system (RAS) and the endothelin system. The function of these systems seems to be fairly well preserved throughout the vertebrate scale, but evolution required several adaptations. Snakes are particularly interesting for studies related to the cardiovascular function because of their elongated shape, their wide variation in size and length, and because they had to adapt to extremely different habitats and gravitational influences. To keep the normal cardiovascular control the snakes developed anatomical and functional adaptations and interesting structural peculiarities are found in their autonomic, KKS, RAS and endothelin systems. Our laboratory has characterized some biochemical, pharmacological and physiological properties of these systems in South American snakes. This review compares the components and function of these systems in snakes and other vertebrates, and focuses on differences found in snakes, related with receptor or ligand structure and/or function in autonomic system, RAS and KKS, absence of components in KKS and the intriguing identity between a venom and a plasma component in the endothelin system. [Copyright &y& Elsevier]

Abstract: Aim: Angiotensin 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 method: Contraction 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 findings: Ang 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. Significance: The 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. [Copyright &y& Elsevier]