HUVECs were treated with 10 nM E2, 100 nM 4-OHT, 100 nM RAL, 100 nM ICI 182,780 or 10 nM E2 and 100 nM ICI 182,780 for 6 d. Complex IV activity was measured as described in Materials and Methods. The EtOH control was set to 1. The EtOH value was originally 1.13 ×10−4 OD/min. Values are the mean of quadruplicate determinations ± SEM. *, p < 0.05 versus EtOH control; ** p < 0.05 versus same treatment without ICI.