Ligand-mediated regulation of kinin receptors in the rabbit

The kinin B-1 receptors (B(1)Rs), stimulated by des-Arg(9)-kinins, are comp letely inducible, notably following treatment of animals with bacterial lip opolysaccharide. Several studies based on cultured cells have suggested a f orm of autoregulation of kinin receptors, because B-2 receptor (B2R) or B1R stimulation could transcriptionally upregulate B1R expression. The B2R may rather be downregulated in inflammatory conditions. A rabbit B2R-green flu orescent protein (GFP) conjugate stably expressed in HEK 293 cells was rapi dly internalized in response to the agonist bradykinin, Ligand-induced rece ptor cycling was documented applying confocal microscopy, The results confi rm agonist-induced B2R endocytosis, but extensive recycling to the cell mem brane does not support agonist-induced downregulation.