Partial agonists and full antagonists at the human and murine bradykinin B-1 receptors

We developed a functional assay to evaluate the activity of kinin peptides at the human and mouse bradykinin (BK) B-1 receptors. The photoprotein aequorin expressed in 293-AEQ17 cells was used to measure calcium mobilization due to activation of the human or mouse B-1 receptors by kinin peptides. The B-1 agonists des-Arg(9)-BK and des-Arg(10)-kallidin activated the human receptor (EC50 = 112 and 5 nM, respectively), whereas the B-1 peptide antagonists des-Arg(9),Leu(8)-BK and des-Arg(10),Leu(9)-kallidin showed no activation. At the murine receptor, the agonists des-Arg(9)-BK and des-Arg(10)-kallidin activated the receptor with EC50 values of 39 and 23 nM, respectively. In contrast, the two peptide antagonists showed significant agonism at the murine receptor. Thirty-nine and 44% agonism of the mouse receptor was observed with des-Arg(9),Leu(8)-BK (EC50 = 56 nM) and des-Arg(10),Leu(9)-kallidin (EC50 = 177 nM). Two recently described kinin analogues, [Lys-Lys(0),Hyp(3),Igl(5),D-Igl(7),Oic(8),des-Arg(9)]BK and [D-Arg(0),Hyp(3),Igl(5)D-Igl(7),Oic(8),des-Arg(9)]BK (B9858 and des-Arg(9)-B9430), failed to agonize the mouse receptor. These peptides were potent antagonists of des-Arg(10)-kallidin- and des-Arg(9)-BK-induced bioluminescence at the cloned human and mouse B-1 receptors.