Functional responses of aequorin-loaded human neutrophils. Comparison with fura-2-loaded cells.

Aequorin-loaded human neutrophils in response to chemotactic peptides and ionomycin showed a sharp rise in their intracellular Ca2+ concentration which decayed within 2 min. Depletion of extracellular Ca2+ suppressed only the ionomycin-induced increase. Fura-2-loaded cells also showed a sharp rise in the intracellular Ca2+ concentration in response to each stimulator, while the decline was extremely slow in the ionomycin-induced Ca2+ increase. Depletion of extracellular Ca2+ reduced the duration of ionomycin-induced Ca2+ increase. Cytochalasin B almost equally potentiated the rise in the intracellular Ca2+ concentration induced by each stimulator. Aequorin-loaded cells showed impaired phagocytotic activity, while degranulation and oxygen radical production were not affected.