Measurement of functional IL-8 receptors by Ca²⁺ mobilization. Purified peripheral blood PMNs suspended in Indo-1AM medium were preincubated with 1,10-phenanthroline (Phen, 0.5 mmol/L), EDTA (5 mmol/L), or bestatin (100 μmol/L) for 30 minutes at 37°C followed by the addition of LPS (100 ng/mL), TNF- (50 ng/mL), or IL-8 (500 ng/mL) for a further 1 hour at 37°C. (A-C) IL-8 (50 ng/mL) or (D) fMLP (5 × 10⁻⁷ mol/L) was added to cells and Ca²⁺ flux was measured.