QUNIACRINE AND OTHER BASIC AMINES IN HUMAN-PLATELETS - SUBCELLULAR COMPARTMENTATION AND EFFECTS ON SEROTONIN

  • 1 January 1984
    • journal article
    • research article
    • Vol. 43  (1) , 25-42
Abstract
Human platelets appear to accumulate quinacrine both in a thrombin-releasable compartment (dense bodies or amine storage vesicles) and in another compartment from which it is released by agents known to collapse pH gradients (possibly lysosomes with an acidic interior). Approximately 61% of the total amount of quinacrine present in human platelets resides in dense bodies and 14% in lysosomes, with the remainder probably present in the cytoplasm. Other basic amines are accumulated in the 3 compartments to widely varying extents, suggesting that several factors besides the existence of pH gradients act to determine the distribution of these substances within the cell. The fluorescence emission of quinacrine excited with 420 nm light is completely quenched for quinacrine inside both dense bodies and lysosomes, and the absorption of 440 nm light is decreased by .apprx. 25%. Quinacrine added to dense bodies at 37.degree. C induces the efflux of 5-hydroxytryptamine (5HT) from the bodies. There is no 5HT loss following quinacrine entry at 0.degree. C, and the relationship between the 2 types of amine movement varies according to incubation time at 0.degree. and 37.degree. C. This action of quinacrine does not appear to be associated with stoichiometric exchange of 5HT and quinacrine, but rather to modulation of the passive permeability of the dense body membrane for 5HT.