CHANGES OF INTRACELLULAR FREE CALCIUM-CONCENTRATION IN HUMAN POLYMORPHONUCLEAR LEUKOCYTES AFTER REPEATED STIMULATIONS WITH N-FORMYL-METHIONYL-LEUCYL-PHENYLALANINE
D. Nowak et al., CHANGES OF INTRACELLULAR FREE CALCIUM-CONCENTRATION IN HUMAN POLYMORPHONUCLEAR LEUKOCYTES AFTER REPEATED STIMULATIONS WITH N-FORMYL-METHIONYL-LEUCYL-PHENYLALANINE, Immunobiology, 192(5), 1995, pp. 343-352
A rapid transient rise in the intracellular free calcium concentration
([Ca2+](i)) is an important step in human polymorphonuclear leukocyte
s (PMNL) activation. This can be caused by many inflammatory mediators
and has been implicated in the regulation of various cellular reactio
ns. In this study we investigated the changes of [Ca2+](i) in human PM
NL activated three times with 10(-7) M n-formyl-methionyl-leucyl-pheny
lalanine (FMLP). PMNL in the presence of 1 mM Ca2+ were able to respon
d to three consecutive stimulations with FMLP. The first Ca2+ response
was the highest one and was a result of Ca2+ release from internal st
ores (which was responsible for about 30% of maximal increment in [Ca2
+](i)) and the extracellular Ca2+ influx. Experiments with PMNL suspen
ded in a medium containing 100 nM Ca2+ and pretreated with 1 mM Ni2+ (
an inorganic calcium channel blocker) revealed that the second and thi
rd response is completely dependent on the extracellular Ca2+ influx.
Changes of the time interval between stimulations had no influence on
the occurrence of extracellular Ca2+ influx related to second addition
of FMLP. Elongation of the time interval up to 30 min did not restore
the release of Ca2+ from internal stores. It indicates the occurrence
of dissociation of Ca2+ release from intracellular stores and extrace
llular Ca2+ influx during the second and third PMNL response to FMLP.