DEVELOPMENT OF A BINDING ASSAY FOR THE B-1 RECEPTORS FOR KININS

A novel binding assay to kinin B-1 receptors was developed, based an the design of a high-affinity agonist ligand, [I-125]Tyr-Gly-Lys-Aca-Lys-des-Arg(9)-BK. Binding to rabbit aortic smooth muscle cells is highly temperature-dependent (optimal at 37 degrees C); apparent binding equilibrium is reached within 30 min, and competition by kinin analogs reveals the expected correlation with the B-1 receptor pharmacology. The dissociation constant (K-d) of the labeled ligand is approx. 0.2 nM and this value does not change significantly as a function of cytokine pretreatment. However, the receptor abundance (B-max) is significantly increased (1.5-fold) by pretreating the cells with interleukin-1 (IL-1), while oncostatin M (OSM) produces a marginal increase of the B-max. This assay may be useful in documenting the regulation of B-1 receptors in pathology.