Hypoxia increases atorvastatin-induced decay-accelerating factor expression. Analysis of decay-accelerating factor expression on human umbilical vein endothelial cells (HUVEC) (a) following 48 hours culture in 21% O2 (open bars) or 1% O2 (filled bars) in the presence or absence of atorvastatin (0.25 μM). (b) and (c) HUVEC were treated with increasing concentrations of atorvastatin for 48 hours in the presence (filled bars) or absence (open bars) of (b) cobalt chloride (CoCl2) (100 μM) or (c) desferrioxamine (DFO) (100 μM). Decay-accelerating factor expression was measured by flow cytometry using the mAb 1H4. Bars represent the mean ± standard error of the mean (n = 4). *P < 0.05, **P < 0.01 compared with untreated controls.