EFFECT OF WIN-64338, A B-2 BRADYKININ RECEPTOR ANTAGONIST ON GUINEA-PIG TRACHEAL SMOOTH-MUSCLE CELLS IN CULTURE

This study investigated the effect of the non-peptidic B-2 bradykinin (BK) receptor antagonist WIN 64338 on BK binding and BK-induced inosit ol phosphate formation on guinea-pig tracheal smooth muscle cells in c ulture. The presence of specific and saturable binding sites for BK wa s demonstrated using [H-3]BK. Scatchard analysis indicates a single po pulation of binding sites for [H-3]BK with a maximal density (B-max) o f 245.4 +/- 71 fmol/mg of protein and an equilibrium dissociation cons tant (K-d) of 87.7 +/- 0.12 pM. The order of potency of B-2 BK recepto r ligands was Hoe 140 = NPC 17731 > BK > WIN 64338 > D-Arg(0)[Hyp(3), D-Phe(7)]-BK > > des-Arg(9)-BK, while the B-1 BK receptor antagonist, des-Arg(9)-[Leu(8)]-BK, was without effect on [3H]BK binding. These re sults demonstrate the presence of B-2 BK receptors on cultured trachea l smooth muscle cells. The cells were stimulated by BK, and inositol p hosphate formation was determined by anion exchange chromatography. Th e stimulating effect of BK on inositol phosphate formation was concent ration dependent (1 nM to 10 mu M). The B-1 BK agonist des-Arg(9)-BK d id not induce inositol phosphate formation. The order of potency of B- 2 antagonists to inhibit BK-induced inositol phosphate formation was H oe 140 = NPC 17731 > WIN 64338 > D-Arg(0)[Hyp(3), D-Phe(7)]-BK. This s tudy demonstrates that WIN 64338 is able to displace [H-3]BK binding a nd to inhibit B-2-BK-induced inositol phosphate formation on cultured guinea-pig tracheal smooth muscle cells. (C) 1998 Elsevier, Paris.