TABLE 1.

Ability of catalase to inhibit production of RNI by activated D9 macrophages is restricted to C-10, the preparation with the lowest specific activity^a

Catalase	Sp act (U/mg of protein)	% Reduction in NO2− production
C-3155	48,700	11.4
C-100	58,000	13.4
C-30	18,600	8.1
C-10	2,600	92.4

^aMacrophages (1.5 × 10⁵ cells per well in 96-well tissue culture plates) were primed with IFN-γ (250 U/ml) for 12 h. The various preparations of catalase were added to cultures at a final concentration of approximately 2,600 U/ml. Four hours later, supernatants were removed and replaced with culture medium containing LPS (1 μg/ml) with or without catalase. Culture supernatants were assayed for NO₂⁻ content 24 h later. Experiments involving catalase preparations C-10 and C-3155 were carried out three times with similar results. Preparations C-100 and C-30 were tested only once. Similar results were obtained using J774.16 and primary peritoneal macrophages.