Synthesis and pharmacological properties of [5-isoleucine]-, [8-isoleucine]-, and [5,8-diisoleucine]bradykinin.

Three bradykinin analogues have been synthesized in which the phenylalanine residue(s) at positions 5 and/or 8 have been substituted by isoleucine. All these analogues have weak bradykinin-like activity in isolated rat uterine smooth muscle or in rat blood pressure assay. No antagonistic activity was observed with any of these analogues. The importance of phenylalanine at positions 5 and 8 is discussed.