bradykinin \bra`dy*ki"nin\ n. a hypotensive tissue hormone ({C50H73N15O11}) which acts on smooth muscle, dilates peripheral vessels and increases capillary permeability. It is formed locally in injured tissue and is believed to play a role in the inflammatory process. It is a nonapeptide with the sequence: Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg. --MI11 Syn: kallidin I; callidin I; kallidin-9. [PJC]