HETEROGENEITY OF HUMAN WHOLE-BLOOD PLATELET SUBPOPULATIONS .3. DENSITY-DEPENDENT DIFFERENCES IN SUBCELLULAR CONSTITUENTS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 64  (1) , 185-193
Abstract
Structurally intact platelet cohorts of differing densities can be isolated from normal subjects by the use of isosmolar arabinogalactan density gradients. Using platelets separated in this fashion, the density-dependent distribution of 4 subcellular organelles was studied: mitochondria, lysosomes, dense bodies, and .alpha. granules. Mitochondria, which are not secreted during platelet release, demonstrate a slow decline in monoamine oxidase activity within the gradient. Lysosomal .beta.-glucuronidase does not vary significantly with platelet density. Dense body number and endogenous serotonin content decrease significantly with decreasing platelet density, primarily as the result of differences in the number of storage organelles. Platelet factor 4 content declines rapidly in comparison to lysosomal activities (P < 0.001 from bottom to top of the gradient), but .beta.-thromboglobulin, also an .alpha. granule component, exhibits considerably less change than platelet factor 4 (P < 0.001). Specific platelet subcellular constituents have different density distributions. These density differences may be due to differential in vivo loss of selective biochemical constituents from unique subcellular compartments.

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