Table 1.

Total and extracellular arginase activity of human red blood cells in presence of heme products or pro- and antioxidant systems

Fraction	Treatment	n	Arginase Activity (U/g Hb) in Controls	Arginase Activity (U/g Hb) After Treatment	Difference [mean (95% CI)]	P Value
Total	FP (40 μM)	12	57.6 ± 15.0	69.5 ± 15.8	11.8 (8.0–15.7)	<0.001
	FP (40 μM) with NAC (5 mM)	5	56.8 ± 8.3	72.0 ± 10	15.2 (9.0–21.5)	0.003
	FP (40 μM) with SZ (100 μΜ)			70.5 ± 8.0	13.8 (9.3–18.2)	0.001
	Fe (0.3 mM)-ascorbate (05 mM)			63.3 ± 3.4	6.5 (0.1–12.9)	0.048
	HP (40 μM)	8	55.5 ± 2.3	71.4 ± 1.7	15.9 (13.3–18.5)	<0.001
Supernatant	FP (40 μM)	6	55.0 ± 12.0	72.2 ± 15.0	17.3 (4.6–30.1)	0.018

Arginine activity values [in μm urea produced/min (U)/g Hb] are means ± SD for n samples. Human red blood cells (RBC) [0% hematocrit (Hct)] were pretreated with Fe(III)-protoporphyrin IX (FP) or hematoporphyrin IX (HP) for 1 h at 37°C or Fe-ascorbate for 3 h at 37°C. After this, RBC were washed twice in PBS-glucose and resuspended at 40% Hct in the same buffer. Arginase activity was assayed in the total suspension or the extracellular medium after 16-h incubation. In a subset, RBC suspensions were exposed for 30 min at 37°C to 5 mM N-acetyl-l-cysteine (NAC) or 100 μM sulfosalazine (SZ) before treatment with FP. Arginase activity was compared in treated samples vs. controls by paired Student's t-test. CI, confidence interval.