Figure 2. Nicotinamide adenine dinucleotide phosphate oxidase activity in membrane preparations of human corneal stromal fibroblasts as assayed by superoxide dismutase-inhibitable cytochrome c. Human corneal stromal fibroblasts were grown in cell culture, harvested, lysed, and the membranous fraction harvested as the 29,000× g pellet, as described in the Methods. Cell lysates were assayed for superoxide production under various conditions: (1) NADPH as substrate, (2) NADPH as substrate in the presence of 100 μM L-NAME, (3) NADPH as substrate in the presence of 50 µM 1400W, (4) NADPH as substrate in the presence of 10 µM diphenyliodonium, (5) NADPH as substrate in the presence of 100 µM allopurinol, and (6) NADH as substrate. Each bar represents the mean specific activity +/- standard deviation (n=3). An asterisk indicates a significant reduction in SOD inhibitable superoxide production, (p<0.001).