Comparison of PAF- and fMLP-induced [Ca2+]i transients in human polymorphonuclear leukocytes.
Changes of [Ca2+]i in human polymorphonuclear leukocytes (PMNL) were studied. PMNL suspension was activated three times every 5 min with 10(-7) M PAF and fMLP. Both PAF and fMLP, induced three consecutive [Ca2+]i transients in PMNL suspended in medium with 1 mM Ca2+. The first Ca2+ response was a result of Ca2+ release from internal stores and the extracellular Ca2+ influx, while the second and third responses were completely dependent on Ca2+ influx from extracellular space. The contribution of Ca2+ from intracellular stores to the first PAF-induced Ca2+ response was about 1.4-fold lower in comparison with the first fMLP induced Ca2+ response (27 +/- 1 vs 37 +/- 6% (p < 0.05). Previous addition of PAF enhanced 3-fold (p < 0.001) the PMNL response to fMLP while cells pretreated with fMLP failed to increase their [Ca2+]i after challenge with PAF. PMNL from 40% of donors did not respond to PAF in the presence of 100 nM Ca2+. However, the cells responding to PAF as the cells treated with fMLP or cyclopiazonic acid released almost the entire Ca2+ from intracellular stores after challenge. Subtraction of mean [Ca2+]i transients in the presence of 100 nM Ca2+ from that obtained in medium with 1 mM Ca2+ showed that, in PMNL stimulated with PAF in contrast to the cells treated with fMLP, the onset of Ca2+ influx from extracellular space precedes Ca2+ release from intracellular stores. These results suggest that PAF-induced Ca2+ influx from extracellular space is at least partly independent of Ca2+ release from intracellular stores.
Nowak
D
D
Department of Pneumology and Allergology, Medical University of Lodz, Poland.
Bialasiewicz
P
P
Antczak
A
A
Krol
M
M
Piasecka
G
G
D001779:Blood Coagulation Factors / Q000494:pharmacology*; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism*; D010972:Platelet Activating Factor; D011956:Receptors, Cell Surface / Q000378:metabolism
D001779:Blood Coagulation Factors; D005456:Fluorescent Dyes; D010972:Platelet Activating Factor; D011956:Receptors, Cell Surface; D009240:N-Formylmethionine Leucyl-Phenylalanine; D002118:Calcium; D016257:Fura-2