NO production in LTB₄-stimulated human PMN (3.5 × 10⁶/mL), measured by the NO-specific electrode. The upper line (A) shows unstimulated PMN, line (B) stimulated PMN, and the line at the bottom (C) stimulated PMN preincubated with L-NMMA (1 mmol/L), performed as detailed in Materials and Methods. The arrow indicates when LTB₄ (100 nmol/L) was added.