Clinical Chemistry, Vol 16, 312-317, Copyright © 1970 by the American Association for Clinical Chemistry

Dopamine Transport in Human Blood

¹ Chemical Laboratory of the Santa Barbara Cottage Hospital Research Institute, Santa Barbara, Calif. 93105.

Distribution coefficients were determined for dopamine equilibrated between human blood cells and plasma or its constituents by direct fluorescent reading of this fluorophore recovered in the aqueous phase of a trichloroacetic acid separation. The fluorescence was activated at 280 nm and read at 320nm. Recovery of dopamine added to blood constituents was 98 to 102%. Dopamine concentrations in the equilibration phases ranged from 1-5µg/ml with 0.2mg of ascorbic acid as antioxidant. Water solubility accounts for approximately half of dopamine distribution in the red cell—plasma system. The other half is distributed between red cell and plasma proteins. Hemoglobin and Cohn fraction IV-4 show dopamine-binding effects. We trapped dopamine in red cell ghosts during hemolysis and demonstrated that it was released after reconditioning of the ghost membrane wall, thus indicating that the red cell wall is permeable to dopamine and that hemoglobin may act as a transport agent. The role of platelets and white cells in dopamine transport requires further study.