Macrovascular dopamine release

S. Kraschinski, A. Epple and B. Nibbio Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA. In an animal model, the American eel, perifused elastic arteries and large veins, but not the heart and organs with extensive microvascular supply (gills and opisthonephric kidney), release spontaneously free dopamine. Only the region of the cardinal vein, which contains the adrenomedullary equivalent, also releases norepinephrine (NE) and epinephrine (E). Ca2+, KCl, and E stimulate dopamine release from the ventral aorta and caudal vein, indicating that this phenomenon is due to secretion and not to washout. E also stimulates NE release from the ventral aorta and caudal vein. In the rat, both aorta and vena cava spontaneously release dopamine and NE. Thus dopamine secretion from large blood vessels may be general in vertebrates. The dopamine response to high physiological concentrations of E in vivo and in vitro suggests that macrovascular dopamine may be involved in local stress responses.