BRADYKININ BINDING-SITES IN HEALTHY AND CARCINOMATOUS HUMAN LUNG

1 Direct ligand binding techniques have been used to compare bradykini n receptors in squamous- or adeno-carcinoma and healthy lung membranes removed from patients during operations. 2 The binding of [H-3]-brady kinin to healthy lung membrane is time-dependent and saturable with a K(D) value of 1.08 +/- 0.18 nM and a B(max) value of 46.1 +/- 3.1 fmol mg-1 protein (n = 10). In squamous-carcinoma tissue (n = 8) the same amount of receptors are present, B(max) = 52.2 +/- 3.3 fmol mg-1 prote in (P = 0.22) but the K(D) value is significantly higher 2.57 +/- 0.40 nM (P = 0.004). Similar measurements were obtained for adeno-carcinom a tissue (n = 3), K(D) = 2.80 +/- 0.29 mM (P = 0.001) and B(max) = 49. 8 +/- 2.1 fmol mg-1 protein (P = 0.56). 3 In both healthy and squamous -carcinoma preparations, bradykinin analogues displace [H-3]-bradykini n binding with the following relative order of potency: Hoe 140 > brad ykinin > kallidin > D-Arg0[Hyp3,D-Phe7]bradykinin >>>des-Arg9-bradykin in. Of the analogues used, bradykinin and D-Arg0[Hyp3,D-Phe7]bradykini n appear to be able to differentiate the bradykinin receptors present in both preparations. 4 It is concluded that bradykinin receptors pres ent in healthy and carcinomatous human lung are of the B2 type.