The vasopressor action of angiotensin in the snake Bothrops jararaca.

1. Carotid blood pressure from anesthetized B. jararaca snakes was recorded in order to study angiotensin action in this reptile. 2. Whereas [Asn1,Val5] AII and AIII were less potent than [Asp1,Ile5] AII and [Asp1,Val5] AII, [Sar1,Ile5] AII was slightly more potent. 3. Captopril abolished the responses to AI (0.01-3 micrograms/kg). 4. [Sar1,Ala8] AII was uneffective but [Sar1,Leu8] AII or phenoxybenzamine were able to reduce AII vasopressor responses. 5. These results led to the conclusion that the vasopressor response of AII in B. jararaca is due to an interaction with its own receptor but, part of the AII receptor population seems to be coupled to the sympatho-adrenal system. Moreover, structural requirements seem to be necessary for the AII response in B. jararaca.