Specific Pressor Activity and Stability of Synthetic Angiotensins

Abstract
Specific pressor activity of Asp1-Val5-angiotensins I and II was determined by a 4-point assay in rats against various synthetic angiotensins. Specific pressor activity of various angiotensins was also obtained from the dose-blood pressure-response (DR) curve, using a single angiotensin sample per rat. Comparison of 2 values showed that 2 angiotensins interacted in the 4-point assay, yielding a potentiation factor of 0.465-1.373. Specific pressor activity from DR curve is more reliable, because 2 angiotensins are not able to interact. Potency ratio on a molar basis of Asp1-IIe5-angiotensin I, Asp1-Val5-angiotensins I and II, Asn1-Val5-angiotensin II (Ciba Lot-094691) and Asp1-Val5-Ser9-angiotensin I against Asp1-IIe5-angiotensin II were 0.76, 0.91, 2.02, 0.50, and 1.39, respectively. Asp1-Val5-angiotensin II had twice the pressor activity of Asp1-IIe5-angiotensin II. Lyophylized Asp1-IIe5-angiotensins I and II kept dessicated at -20.degree. C, were stable for 27 mo. Solutions of 100, 10 and 0.8 .mu.g/ml were stable for 12, 8 and 6 mo. at -20.degree. C, respectively.

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