HIGHLY SELECTIVE BRADYKININ AGONISTS AND ANTAGONISTS WITH REPLACEMENTOF PROLINE RESIDUES BY N-METHYL-D-PHENYLALANINE AND N-METHYL-L-PHENYLALANINE

For further studies on the structural and conformational requirements of positions 2, 3, and 7 in the bradykinin sequence, we replaced the p roline residues by the more hydrophobic and conformationally restricte d N-methyl-L- and D-phenylalanine (NMF). The biological activities of the new analogs were evaluated on rat uterus, guinea pig ileum, and gu inea pig lung strip. Receptor binding of the analogs was studied in me mbranes from rat uterus and guinea pig ileum. Influence of bradykinin analogs on the release of cytokines from mouse spleen cell cultures wa s also measured. Bradykinin analogs were synthesized by the solid phas e method, using Boc strategy on PAM or Merrifield resins. The best res ults in the formation of the N-methylamide bond were obtained with the coupling reagent PyBrop. In position 7 the substitution of D-Phe by D -NMF, retaining the configuration of the amino acid, converts bradykin in antagonists into agonists. The bradykinin analogs with D-NMF at pos ition 7 gave the highest known tissue selectivity for rat uterus among agonists. [L-NMF(2)]bradykinin has moderate agonist activity on rat u terus but antagonist activity on guinea pig lung strip. It represents a new antagonist for B-2 receptors without any replacement at position 7. The same analog completely inhibits bradykinin-evoked cytokine exp ression by mononuclear cells.