Identification and characterization of B2 bradykinin receptors in sheep nasal turbinate membranes

Abstract

Because bradykinin (BK) has been implicated as a mediator of upper respiratory tract symptomatology, specific 3H-BK binding was investigated in membrane homogenates prepared from sheep nasal turbinate tissue in order to identify and characterize the BK receptor subtype(s) present. 3H-BK saturation and Scatchard analyses revealed a single, high affinity, saturable site (KD of 0.098 nM) with a density of 0.44 pmol/g wet weight tissue. Competition experiments using B1 and B2 receptor agents revealed a B2-BK receptor pharmacology; the B2 agents BK, Lys-BK, NPC-567, [D-Phe7]-BK and [Thi,5,8 D-Phe7]-BK displayed nM affinity while the B1 agents [des-Arg9]-BK and [Leu,8 des-Arg9]-BK competed in the uM range. The absolute and rank order of affinities in this tissue paralleled that found in the guinea pig ileum. No specific binding was found using the putative B1 receptor radioligand 3H-[des-Arg9]-BK. Specific B2-BK receptor binding was not effected by the addition of non-hydrolyzable guanine or adenine nucleotides. These data confirm the presence of B2-BK receptors in this tissue and provide support for a role of BK in nasal function.