Macrophages produce nitrite, nitrate and nitrosamines after addition of catalase

Mouse macrophages produced nitrite and N-nitrosomorpholine after incubation with catalase. A macrophage cell line, J774.1 (1 x 10(6) cells/ml), was incubated with catalase (500 U/ml) and morpholine (5 mM); after 48 h incubation at 37 degrees C, macrophages produced nitrite (100 microM) and N-nitrosomorpholine (1 microM). Stimulation of J774.1 cells with catalase enhanced interleukin-1 production and tumour-killing activity against mastocytoma P815 cells. Flow cytometric analysis showed that catalase was bound to the surface of the macrophages.