Effect of Bcl-xL BH44–23 (BCL; 5 × 10−2 μg/ml) on ATP release from human erythrocytes incubated with iloprost (1 μM, n = 7; A) or UT-15C (1 μM, n = 6; B). Erythrocytes were incubated with BCL or its vehicle, DMF, for 25 min before addition of the prostacyclin analog. Values are means ± SE. †Different from respective baseline and iloprost or UT-15C in the presence of BCL (P < 0.01); n, the number of different individuals studied. RBCs, red blood cells.