Comparison of the X537A-induced ionophoric removal of serotonin and tryptamine from intact human platelets.

In the absence of appreciable dense-body release from platelets, X537A causes rapid movement of 90--95% of vesicular H3-5HT into the extracellular medium. X537A can in addition transport to the extracellular medium 20% of the total tryptamine sequestered in platelets. Investigation of the extraction of aqueous 5HT and tryptamine into a chloroform phase, and the subsequent extraction of each of the two amines from a chloroform to an aqueous phase, suggest that 5HT, but not tryptamine, is transported efficiently between aqueous phases through a non-polar solvent. The observed differences in the movement of the two amines through platelet membranes may be attributable to a similar phenomenon.