Role of membrane potential in the regulation of lectin‐induced calcium uptake

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Abstract
Incubation of lymphocytes with mitogenic lectins triggers Ca2+ uptake. This increase in free cytoplasmic Ca2+ is postulated to be an important signal in the initiation of DNA synthesis. Transmembrane fluxes of monovalent ions and changes in membrane potential are also associated with lectin‐induced activation of lymphocytes. We have examined the relationship between extracellular monovalent ion substitution, the associated electrical potential changes (measured with cyanine dyes), phytohemagglutinin‐induced Ca2+ uptake (measured with Quin‐2) and proliferation in human T cells. The results show that (1) the magnitude of the increase in free cytoplasmic Ca2+ concentration is correlated with the extent of the lymphoproliferative response, (2) lectin‐induced Ca2+ fluxes are sensitive to membrane potential, decreasing with depolarization, and are likely conductive, and (3) the presence of extracellular Na+ during incubation with phytohemagglutinin is not essential to mitogenic triggering.