POTENTIATION OF BRADYKININ WITH SYNTHETIC PEPTIDES ON GUINEA PIG ILEUM

Potentiation of the activity of bradykinin on the isolated guinea pig ileum was studied using a designed test system with the synthetic peptides Leu-Val-Glu-Ser-Ser-Lys, Thr-Pro-Val-Ser-Glu-Lys, derivatives of the former coupled to the N- and C-terminals of bradykinin and two peptides with phenylalanine substituted with its isomer l -3-amino-3-phenylpropanoic acid in the 5- and 5,8-positions in bradykinin respectively. On average, two times potentiation effects were obtained at 10^-6 to 10^-8 M concentrations of the peptides. After elimination of the basic lysine no potentiation occurred with synthetic Leu-Val-Glu-Ser-Ser. With the [βPhe^5,8]-bradykinin a mixed sensitizing/potentiating effect was observed, suggesting that a separation of the two effects may be difficult with an intact receptor structure of this kind. This peptide was not hydrolyzed by carboxypeptidase B or chymotrypsin.