[Specific antagonism between angiotensin II and several of its analogs]

The authors studied comparatively the properties of two angiotensin II analogues, a new compound (1-hydantoin acid, 5-valine, 8-alanine)-angiotensin II (compound III) and (1-asparagine, 5-valine, 8-alanine)-angiotensin II (compound II), as of the myotropic action of angiotensinamide (these experiments were conducted on the rat isolated ascending colon); pressor action of the hormone was investigated in experiments on anesthetized rats. A competitive character of the antagonism--within the range of low concentrations of the analogues--10(-10)--10(-9) M/l--was revealed in vitro. No antagonism was expressed against the nonspecific myotropic agents--acetylcholine and bradykinin. In vivo compounds II and II manifested the antagonistic action against angiotensinamide beginning from the doses of 100 and 50 gamma/kg, respectively.