Cell lysates prepared from control or hemin-treated cells (100 μm for 6 hr) were incubated with 2 μm hemin or biliverdin in the presence of 1 mm NADPH for determination of HO or biliverdin reductase activity, respectively. Bilirubin formation was quantified by HPLC as described in Experimental Procedures. Values are mean ± standard deviation of three (HO) or four (biliverdin reductase) individual experiments.

• ↵1-a Significantly different from control (p < 0.01).