Figure 3.

Basal endoplasmic reticulum (ER) and mitochondrial Ca²⁺ stores are not altered in cells expressing the Bcl-2 SNP variant AA. (A, B) Typical Ca²⁺ traces (A) and per-patient averages (B) of low-affinity fura-2FF fluorescence emission (ratio 340/380 nm) from AA and GG BLCL permeabilized with digitonin (10 μg/mL) in an intracellular buffer (ICB) supplemented with 500 μmol/L adenosine triphosphate. Fluorescence gradually increased to a steady-state maximum that reflects the level of luminal ER Ca²⁺(23). Basal ER free Ca²⁺ was similar in Bcl-2 SNP variants AA and GG. (C) Total ER and mitochondrial matrix calcium concentrations, as measured by electron probe microanalysis, were similar in variants AA and GG, although the former was tenfold higher. (D, E) Electron micrographs of BLCL perinuclear regions. Left panel is a conventionally fixed and embedded specimen; right panel is a rapidly frozen, cryosectioned, and freeze-dried preparation as used for electron probe microanalysis. Both panels illustrate typical organelle abundance and distribution, including ER (arrows) and mitochondria (arrowheads). Bar = .5 μm for both panels. ECB, extracellular buffer; other abbreviations as in Figure 1.