A, KB-3 cells were untreated or treated with 30 nM vinblastine (VBL) for the times indicated and subjected to immunoprecipitation with anti-Bax 6A7 antibody (lanes 3, 6, and 9), followed by immunoblotting for Bax. Precipitates prepared in the absence of 6A7 antibody (lanes 2, 5, and 8) and whole cell extracts (lanes 1, 4, and 7) were also examined as controls. B, KB-3 cells were treated with vinblastine (VBL, 30 nM) for the times indicated, permeabilized, treated with digitonin in the absence or presence of 1 mM DSP, and CHAPS-solubilized particulate fractions subjected to SDS-PAGE. Immunoblotting for Bax was performed with the monomeric (21-kDa) and oligomeric (42-kDa) forms shown.