Elevation of intracellular Ca²⁺ is required for IL-8 secretion.

(A-B) Indo-1/am–labeled neutrophils were stimulated with SAA (1 μM) in the absence (A) or presence (B) of BAPTA/am (20 μM). Triton X-100 was then added to 0.1% for measurement of total intracellular Ca²⁺, an indicator of Indo-1/am equal loading. Relative intracellular Ca²⁺ concentration was expressed as fluorescence ratio (405:485 nm). (C) Secretion of IL-8 and phosphorylation of ERK1/2 by SAA-stimulated neutrophils were determined in the absence or presence of BAPTA/am (20 μM and 40 μM). Maximal secretion (580 pg/mL/10⁶ cells) was set as 100%. Data are presented as means ± SEM of 3 independent experiments, each performed in duplicate.