FIGURE 5.
pH differentially regulates microsomal Ca2+ when BI-1 is overexpressed. A, mag-Fura-2/AM-loaded microsomal fractions were isolated from untransfected, Neo-, BI-1-, and CΔ-BI-1-transfected cells and treated with acidic condition (pH 5.4) at the time indicated. B, the decrease in microsomal Ca2+ induced by acidic pH in A was expressed as a percentage of the maximum releasable Ca2+. C, Fura-2/AM-loaded cells were treated with nigericin (5 μm) in Ca2+-free extracellular medium (pH 6.4), and the increase of [Ca2+]c was measured. Results shown in B and C represent the mean ± S.E. of four independent experiments (*, p < 0.05 compared with Neo cells). UT, untransfected; cyto, cytosolic.