Abstract
To investigate the relationship between different intracellular Ca 2+ pools, cytosolic free calcium ([Ca 2+] i) was surveyed by means of a Fura-2 fluorescence ratio method on single isolated human leukocytes. Both monocytes and neutrophilic granulocytes (PMN) displayed long lasting spontaneous [Ca 2+] i transient changes (1–2 min). In PMN stimulated with the bacterial peptide fMLP we observed transients with shorter duration (10–30 s) and smaller amplitude often superimposed on the long lasting transients. The time course of changes in [Ca 2+] i was recorded in a large number (149) of single leukocytes prestimulated for 5 min with fMLP and then challenged with thapsigargin (a blocker of Ca 2+ uptake in intracellular pools). Statistical analysis of [Ca 2+] i responses revealed that fMLP-sensitive pools contributed to the long lasting [Ca 2+] i transients seen in both leukocyte types. However, the existence of fMLP-insensitive calcium pools may explain the superimposed transients seen in PMN. Thapsigargin was also added together with EGTA (to impede contribution from extracellular Ca 2+) to 198 fMLP prestimulated and 153 unstimulated PMN. Based on Ca 2+ reglstrations in these cells and a mathematical model (supposing two separate first order responses) the amount of Ca 2+ stored in the various pools and their release kinetics were estimated. The results indicate that fMLP-insensitive calcium pools exist in PMN but not in monocytes. Since the digital imaging technique also depicts cellular motility, an additlonal finding was that the leukocyte's ability to sequestrate the Ca 2+ from the cytosol seemed important to locomotion.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call