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Arachidonic acid activates Ca2+ extrusion in macrophages
C Randriamampita1, A Trautmann
1Laboratoire de Neurobiologie, Ecole Normale Supérieure, Paris, France.
The Journal of Biological Chemistry
|October 25, 1990
Summary
Platelet-activating factor (PAF) stimulates calcium (Ca2+) efflux in macrophages, independent of initial intracellular calcium increases. Arachidonic acid, produced after PAF stimulation, plays a key role in regulating this calcium extrusion.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Platelet-activating factor (PAF) is known to increase intracellular calcium concentration (Ca2+i) in macrophages.
- The sustained increase in Ca2+i involves a balance between calcium influx and efflux.
- Understanding calcium regulation is crucial for macrophage function.
Purpose of the Study:
- To investigate the mechanism of PAF-induced calcium efflux in macrophages.
- To determine if PAF-evoked calcium extrusion is a consequence of elevated Ca2+i.
- To identify the role of arachidonic acid in PAF-mediated calcium regulation.
Main Methods:
- Single-cell monitoring of intracellular calcium concentration (Ca2+i) using the dye Fura-2.
- Stimulation of macrophages with PAF and thapsigargin.
- Assessment of calcium extrusion using exogenous arachidonic acid and inhibitors.
Main Results:
- PAF induced calcium efflux in thapsigargin-treated macrophages without a preceding Ca2+i rise.
- PAF-evoked calcium extrusion was not mediated by the Na+/Ca2+ exchanger.
- Exogenous arachidonic acid induced calcium efflux, and this process was blocked by inhibiting phospholipase A2, suggesting arachidonic acid's involvement.
Conclusions:
- PAF-induced calcium extrusion in macrophages can occur independently of an initial increase in intracellular calcium.
- Arachidonic acid, produced following PAF stimulation, is implicated in regulating a calcium extrusion system, likely a Ca2(+)-ATPase.