Two different types of receptors for bradykinin have been found in isolated veins of the rabbit. The first receptor is a stable component of the smooth muscle membrane and it is found in the jugular vein, while the second is generated de novo during incubation in vitro and it is present in the mesenteric vein. Actinomycin D and cycloheximide block the generation of receptors in the mesenteric vein, without exerting any action either on receptors for other agonists (e.g. substance P) in the same tissue, or on the other receptor for bradykinin in the jugular vein.