CHARACTERIZATION OF THE BRADYKININ RECEPTOR IN THE HUMAN NASAL AIRWAYUSING THE BINDING OF [I-125]HOE-140

1 The aim of this study was to characterize the kinin receptor in the human nasal airway using [I-125]Hoe 140 binding to a membrane preparat ion from human nasal turbinates and to compare Ki values from binding displacement by antagonists with the functional effects of these drugs in vivo. We also investigated the effect of Hoe 140 ([D-Arg(0), Hyp(3 ), Thi(5), D-Tic(7), Oic(8)]-bradykinin), on bradykinin release into t he nasal airway. 2 In a membrane preparation from human nasal turbinat es removed during surgery, [I-125]-Hoe 140 labelled a single, saturabl e binding site. The equilibrium dissociation constant (at 20 degrees C ) for [I-125]-Hoe 140 binding to the receptor was 0.46+/-0.08 nM. The B-max was 0.136+/-10.003 pmol mg(-1) protein and the Hill coefficient was 1.01+/-0.07. 3 The association rate constant for [I-125]-Hoe 140 b inding to the receptor was 0.20+/-0.06 nM(-1) min(-1) and the dissocia tion rate constant was 0.14+/-0.01 min(-1). These values were determin ed at 4 degrees C. The equilibrium dissociation constant calculated fr om these rate constants was 0.70 nM. 4 Bradykinin and the B-2 receptor antagonists, NPC 567, NPC 17731, NPC 17761, [1-adamantane acetyl-D-Ar g(0), Hyp(3), Thi(5,8), D-phe(7)]-bradykinin, WIN 64338 and Hoe 140 di splaced [I-125]-Hoe 140 binding: the K-1 values from binding displacem ent are consistent with values expected from a B-2 receptor. The B-1 a gonist, [des-Arg(9)]-bradykinin and the B-1 antagonist, [des-Arg(9)]-H oe 140 failed to displace [I-125]- Hoe 140 binding at concentrations u p to 1 mu M. 5 The bradykinin antagonist, Hoe 140, 10 to 200 mu g, giv en by intranasal aerosol, produced a dose-related inhibition of the re duction in minimal nasal cross-sectional area (Amin) induced by bradyk inin in normal subjects and by house dust mite antigen in subjects wit h allergic rhinitis to house dust mite. Hoe 140, 10 to 200 mu g, also caused a dose-related inhibition of the release of albumin into the na sal cavity following challenge with bradykinin. 6 [1-Adamantane acetyl -D-Arg(0), Hyp(3), Thi(5,8) D-Phe(7)]-bradykinin, 30 to 200 mu g, caus ed a dose-related inhibition of the reduction in Amin and the release of albumin into the nasal cavity induced by bradykinin. NPC 567 ([D-Ar g(0), Hyp(3), D-Phe(7)]-bradykinin) failed to inhibit the reduction in Amin or the release of albumin into the nasal cavity at a dose of 10 mg. 7 Challenge of allergic subjects with house dust mite antigen caus ed a significant elevation of the bradykinin concentration in nasal la vage fluid and a reduction in Amin, Hoe 140, 100 mu g, prevented the a ntigen-induced reduction in Amin and also abolished the antigen-induce d increase of bradykinin in nasal lavage fluid. 8 We conclude that the re is a B-2 bradykinin receptor in the human nasal airway which mediat es nasal blockage and plasma extravasation induced by either bradykini n or antigen challenge. It is possible that Hoe 140 inhibits kallikrei n in the human nasal airway as well as blocking the B-2 receptor.