[³H]bradykinin receptor binding in mammalian tissue membranes

[³H]Bradykinin binds to membranes from a variety of mammalian tissues in a saturable fashion with a dissociation constant of about 5 nM. Highest levels of binding are detected in guinea pig ileum, colon, and duodenum and in the estrous rat uterus. The relative potencies of bradykinin derivatives in competing for these binding sites in guinea pig ileum membranes correlate with their contractile potencies in the ileum better than with contractile effects in the uterus. Thus, receptor recognition sites may differ in ileum and uterus. Monovalent and divalent and divalent cations at physiological concentrations reduce [³H]bradykinin binding. Of the monovalent cations, sodium lowers binding 50% at about 80 mM. Among the divalent cations, calcium lowers binding about 50% at 5 mM, suggesting a link to the calcium conductance channel.