MACROVASCULAR DOPAMINE RELEASE

In an animal model, the American eel, perifused elastic arteries and l arge veins, but not the heart and organs with extensive microvascular supply (gills and opisthonephric kidney), release spontaneously free d opamine. Only the region of the cardinal vein, which contains the adre nomedullary equivalent, also releases norepinephrine (NE) and epinephr ine (E). Ca2+, KCl, and E stimulate dopamine release from the ventral. aorta and caudal vein, indicating that this phenomenon is due to secr etion and not to washout. E also stimulates NE release from the ventra l aorta and caudal vein. In the rat; both aorta and vena cava spontane ously release dopamine and NE. Thus dopamine secretion from large bloo d vessels may be general in vertebrates. The dopamine response to high physiological concentrations off in vivo and in vitro suggests that m acrovascular dopamine may be involved in local stress responses.