Figure 1.

Ba²⁺ inhibits exchange-mediated ⁴⁵Ca²⁺ uptake by CK1.4 cells. (Left) Cells were pretreated with 0.4 mM ouabain and assayed for ⁴⁵Ca²⁺ uptake (15 s) in NMDG-PSS containing the indicated concentrations of BaCl₂. The concentrations of ⁴⁵Ca²⁺ used are 1 mM (filled circles) and 0.1 mM (open circles). (Right) The data from the left panel for 1–10 min are presented as a Dixon plot. The point of intersection of the two lines yields an apparent K _i for Ba²⁺ of 3 mM (n = 5).