Subcellular distribution of transferrin-bound zinc incorporated by phytohemagglutinin-stimulated and unstimulated human lymphocytes.

The distribution of transferrin-bound zinc incorporated by phytohemagglutinin-stimulated and unstimulated human lymphocytes has been studied as a function of time in four subcellular fractions (nuclei, mitochondria, microsomes, and soluble). In untreated lymphocytes, the percent of total incorporated zinc in each fraction remains relatively constant over 72 h in culture. However, there is a time-dependent change in the percent of total incorporated zinc in all fractions isolated from phytohemagglutinin-stimulated cells, and this change is most apparent for the nuclear and soluble fractions. Apparently some sustained production of energy is required for this change in subcellular distribution of zinc to occur. Additionally, the uptake of cytoplasmic zinc by purified lymphocyte nuclei has been studied. Uptake is rapid and occurs maximally under conditions known to be optimal for stimulation of nuclear adenylate cyclase.