Choline uptake is increased by Ca++ and liposomes+ Ca++ in ascites tumor cells.

Steady-state uptake of choline by Lettre-Ehrlich tumor cells in vitro, resulting in cell-to-medium ratios of 10 or more, is significantly increased by 0.2―1.0 mM Ca ++ as well as by dipalmitoyl phosphatidyl choline multilamellar liposomes+Ca ++ . The increases occur in spite of a decrease in carrier affinity, as indicated by the K m , and therefore result either from increased carrier velocity or utilization of new carriers