Release of Conjugated Catecholamines by the Adrenal Medulla Equivalent of the American Eel, Anguilla rostrata

The in vivo perfusate of the cardiovascular system of the American eel (Anguilla rostrata) contains both free and conjugated fractions of dopamine, norepinephrine, and epinephrine. In vitro perifusion revealed that conjugated catecholamines are released from the adrenal medulla equivalent. Together with similar reports on mammals, this suggests that conjugated catecholamines are phylogenetically wide-spread components of the secretory cocktail of chromaffin cells. The present findings are compatible with an "active" role of the catecholamine conjugates.