Figure 1. Nicotinamide adenine dinucleotide phosphate-dependent superoxide production by human corneal stromal fibroblasts. Cells were grown in cell culture, harvested, and permeabilized with streptolysin O. The permeabilized cells (2.5×10⁵) were incubated in 3-morpholinopropane-1-sulfonic acid (MOPS) buffer in the presence and absence of 200 units of superoxide dismutase (as described in the Methods). Reactions were initiated by the addition of (●) 200 µM NADPH, (○) 200 µM NADH, or (▼) no substrate. The superoxide dismutase-inhibitable change in optical density at 550 nm (OD₅₅₀) is plotted verses time for 2.5×10⁵ cells.