Inhibition of mitochondrial-specific protein symthesis in human lymphocytes and platelets is dependent upon the stage of cellular differentiation.

Small lymphocytes differentiate into functionally active blast cells in vitro upon stimulation with such mitogens as phytohemagglutinin and sodium periodate. If stimulated lymphocytes are subsequently treated with the nucleic acid intercalating dye ethidium bromide, electron-dense complexes containing nucleic acid are formed in mitochondria, protein synthesis in mitochondria is inhibited, and lymphoblast division ceases. Formation of complexes and the development of morphologically abnormal mitochondria provide ultrastructural evidence of mitochondrial protein inhibition and serve as markers for mitogen-responsive lymphocytes. The formation of these abnormalities in all mitochondria of treated megakaryocytes and 22% of mitochondria in platelets indicates that platelets contain functional nucleic acid and that the induced structural changes may be occurring in a less-differentiated (i.e., younger) subpopulation of circulating platelets.