An active transport of serotonin was demonstrated in a previous report from this laboratory on rabbit blood platelets. Epinephrine is known to be taken up by the blood platelets as serotonin when the cells are suspended in plasma. In this paper evidence of an active transport of epinephrine is presented. The absorption of this amine is the movement into the cell against a concentration gradient. Epinephrine added to the suspending medium accumulated in the cells, after 1 hour's incubation at 37°C, when glucose or its metabolites were present. The concentration of the amine rose to 1 or 2 µg from about 0.005 µg/mg dry weight of platelets. Glucose, pyruvate, acetate, α-ketoglutarate and fumarate were the effective stimulators. The effect of glucose was diminished by the presence of sodium fluoride, iodoacetate, 2,4-dinitrophenol and reserpine. Competitive inhibitions of the active transport by aromatic compounds containing ethylamine groups might suggest the participation of the amine group of epinephrine in its transport. In contrast, serotonin transport was inhibited by a 5-hydroxyindol compound.
Effect of EGTA on serotonin transport into blood platelets.
