Inhibition by SQ 20881 of vasopressor response to angiotensin I in conscious animals

A synthetic nonapeptide structurally identical to one of the compounds found in the venom of Bothrops jararaca was studied in unanesthetized rats and dogs. The nonapeptide, administered by various routes, inhibited the vasopressor response induced by angiotensin I, but not that by angiotensin II, in unanesthetized normotensive dogs, and in unanesthetized normotensive or spontaneously hypertensive rats. The activity was presumably the result of inhibition of angiotensin-converting enzyme. This peptide also augmented bradykinin-induced vasodepression in both species.Repeated daily administration of this synthetic nonapeptide for 5 days did not produce tolerance.