ABSTRACT

The main stimuli for the release of endothelium-derived vasoactive factors appear to be local in origin. Among these, the events associated with the coagulation of blood most likely take a prominent position. In rings of the aorta of the rabbit and the rat, inhibitors of endothelium-derived relaxing factor (EDRF) cause increases in tension in the absence of substances known to evoke endothelium-dependent relaxations. The action of basally released EDRF is prevented by hemoglobin and methylene blue. When canine arteries with endothelium are perfused under control conditions, the perfusate contains relaxing factors which can be bioassayed. The perfusate of cultured porcine aortic endothelial cells, in the majority of cases, also relaxes bioassay rings. Bradykinin is formed in the blood and the kidney upon activation of the kinin system; it contributes to the regulation of the secretion of exocrine glands. Bradykinin causes endothelium-dependent relaxations in many blood vessels including cerebral arteries.