Relative biological activities of Asn1-,Val5-angiotensin II, Ile5-angiotensin II and Sar1-angiotensin II in man

Biological activities of asn1-,val5-angiotensin II (Hypertensin, Ciba, Asn1-,Val5-ANG II), ile5-angiotensin II (human angiotensin II, Ile5-ANG II) and sar1-angiotensin II (Sar1-ANG II) were compared in man. In 7 normal men 5 pmol/kg X min each of Asn1-,Val5-ANG II, Ile5-ANG II and Sar1-ANG II was infused iv from 0900 h to 0930 h at 1-week intervals. Average increments of blood pressure at the end of the infusions were 11/12, 23/20 and 36/30 mmHg, respectively (significant differences among the 3: P less than 0.001), average decrements of plasma renin activity were 0.30, 0.32 and 0.27 ng/ml X H, respectively (no significant difference among the 3), average increments of plasma aldosterone were 1.1, 2.3 and 4.4 ng/100 ml, respectively (significant difference between the former 2: P les than 0.001, between the latter 2: P less than 0.02), and durations of blood pressure rise after the cessation of these infusions (T) were 2-5 (average 5) min, 10-25 (average 20) min and 35-60 (average 40) min, respectively (significant difference between the former 2:less than P 0.01, between the latter 2: P less than 0.001). From these results it is evident that the pressor and steroidogenic actions of Ile5-ANG II are significantly stronger than those of Asn1-,Val5-ANG II and that the duration of pressor action of the former is much longer than that of the latter. Therefore, when the activities of angiotensin II (ANG II) derivatives are compared with those of ANG II in man, Ile5-ANG II--natural human ANG II--should always be used instead of Asn1-,Val5-ANG II. The pressor and steroidogenic actions and T of Sar1-ANG II are significantly stronger or longer than those of Ile5-ANG II. The reason for this is thought to be that Sar1-ANG II is bound tightly to the vascular and adrenal ANG II receptors and is not readily metabolized.