In vitro and in vivo studies of (1-sarcosine, 8-threonine) angiotensin II.

The capacity of (1-Sarcosine, 8-Threonine) angiotensin II to block the contractile and pressor effects of exogenous and endogenous angiotensin II was examined. In isolated rabbit aorta, the pA2 value (from pA2 plots) for the analog was 8.75 +/- 0.11. Both the maximum response and the slope of the dose-response curve to angiotensin II were unchanged by the analog. In ganglion-blocked vagotomized rats, infusion of the analog produced a dose-dependent blockage of the angiotensin II pressor effect. In these rats, the analog displayed less agonistic activity than that of (1-Sarcosine, 8-Isoleucine) and (1-Sarcosine, 8-Alanine) angiotensin II. In two-kidney hypertensive rats, the angiotensin II antagonist significantly reduced the arterial blood pressure. The results indicate that (1-Sar, 8-Thr) angiotensin II is a potent antagonist of angiotensin II with less inherent agonistic activity than previously reported analogs.