Figure 10.

Expression of CALX in Xenopus oocytes. Sets of oocytes were microinjected, incubated for several days, loaded with intracellular sodium, challenged with ⁴⁵Ca²⁺ along with a variable monovalent cation, and allowed to take up ⁴⁵Ca²⁺ via reverse Na-Ca exchange for 10′. The concentration of ⁴⁵Ca²⁺ used (5.9–6.9 μM) is indicated for each oocyte set. After uptake, oocytes were rinsed and individually assayed by scintillation counting. “Injected” refers to the substance injected; X_o⁺, the primary monovalent cation placed outside the oocytes being assayed for ⁴⁵Ca²⁺ uptake; X_i⁺, the primary monovalent cation loaded into the oocytes; “No. inj.,” the number of oocytes injected with a particular solution; “Uptake of Ca²⁺ in pmol/oocyte, mean ± σ_n−1,” the mean quantity and SD of ⁴⁵Ca²⁺ taken up per oocyte. “Ch” denotes cationic choline; (−) denotes oocytes left unloaded by outside cations.