Characterization of a new kinin potentiating peptide obtained from human plasma proteins

Partially purified kinin potentiating peptide (KPP) obtained from kininogen-depleted human plasma inhibited lung angiotensin converting enzyme in vitro and potentiated guinea-pig ileum contractions induced by bradykinin (BK), Lys-BK, Met-Lys-BK, Ile-Ser-BK, and Lys-Lys-BK. Contractions evoked by angiotensin II, histamine, acetylcholine, and barium chloride were not potentiated. KPP also potentiated kinin-induced contractions of rat uterus and of guinea-pig ileum pre-incubated with 1,10-phenanthroline. It is suggested that KPP potentiation is due, at least in part, to a direct effect on kinin receptor(s).