EVALUATION OF THE UPTAKE OF VARIOUS AMINES INTO STORAGE VESICLES OF INTACT HUMAN PLATELETS

Abstract

The uptake of various 3H‐labelled amines into a thrombin‐releasable compartment of human platelets, thought to represent the platelet vesicular storage pool, has been evaluated. Measurable amounts of 5‐hydroxytryptamine (5‐HT), dopamine, tyramine, octopamine, and tryptamine accumulate in this pool, and also in a non‐thrombin‐releasable (cytoplasmic) pool during a 30 min incubation period with 10−5 M extracellular amine concentrations. No differences in the accumulation of vesicular or cytoplasmic 5‐HT, dopamine, and tyramine are found in platelets treated with deprenyl to inhibit platelet monoamine oxidase as compared to controls. Extracellular tyramine or dopamine in concentrations as high as 10−5 M does not alter the initial rate of 5‐HT uptake across the platelet plasma membrane. Similarly, sizable cytoplasmic pools of either amine do not alter the initial rate at which small amounts of 5‐HT enter platelet cytoplasm or storage vesicles. 5‐HT thus appears to be the preferred substrate for uptake into platelets and for movement from cytoplasm to vesicles. 1977 British Pharmacological Society