Saralasin (Sar 1, Ala 8, angiotensin II) is an intravenously administered, competitive antagonist of angiotensin II that is used to identify renin-dependent (angiotensinogenic) hypertension. It is soon to be made available for general use as a screening test in patients with suspected renovascular hypertension.
Although several analogues of angiotensin II have been synthesized, the widest clinical experience has been with saralasin. The octapeptide sequences of angiotensin II and saralasin are compared in the Table. The substitution of sarcosine for aspartic acid in position 1 allows saralasin to bind more firmly to angiotensin receptors and to have a longer duration of action,1,2 whereas the substitution of alanine for phenylalanine in position 8 ensures that the interaction of saralasin with the receptors produces a substantially smaller stimulatory effect than that of angiotensin II.2
Since saralasin works through competitive inhibition of angiotensin II,3 its effects are best explained by an