PATHOPHYSIOLOGIC SIGNIFICANCE OF FREE AND CONJUGATED DOPAMINES IN CONGESTIVE-HEART-FAILURE

Sulfoconjugated dopamine constitutes the major portion of circulating or excreted dopamine, but its physiologic significance is still unknow n. To test whether conjugated dopamine serves as a source of free dopa mine in response to acute stress, plasma concentrations of free and co njugated dopamine were measured during an acute exacerbation of heart failure. The plasma concentration of conjugated dopamine decreased sig nificantly during the acute phase of heart failure, whereas that of fr ee dopamine increased. The plasma concentration of free dopamine decre ased, whereas the concentration of conjugated dopamine increased as he art failure improved. An infusion of dopamine increased the plasma con centration of conjugated dopamine, suggesting that at least part of th e excess active dopamine was detoxified through conjugation. The resul ts of these tests with both conjugated and free dopamine are interconv ertible and indicate that conjugated dopamine can serve as a reservoir of active dopamine.